System Catalogs

The system catalogs are the place where a relational database management system stores schema metadata, such as information about tables and columns, and internal bookkeeping information. QHB's system catalogs are regular tables. You can drop and recreate the tables, add columns, insert and update values, and severely mess up your system that way. Normally, one should not change the system catalogs by hand, there are normally SQL commands to do that. (For example, CREATE DATABASE inserts a row into the pg_database catalog — and actually creates the database on disk.) There are some exceptions for particularly esoteric operations, but many of those have been made available as SQL commands over time, and so the need for direct manipulation of the system catalogs is ever decreasing.

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Overview

Table 1 lists the system catalogs. More detailed documentation of each catalog follows below.

Most system catalogs are copied from the template database during database creation and are thereafter database-specific. A few catalogs are physically shared across all databases in a cluster; these are noted in the descriptions of the individual catalogs.

Table 1. System Catalogs

Catalog Name	Purpose
pg_aggregate	aggregate functions
pg_am	relation access methods
pg_amop	access method operators
pg_amproc	access method support functions
pg_attrdef	column default values
pg_attribute	table columns (“attributes”)
pg_authid	authorization identifiers (roles)
pg_auth_members	authorization identifier membership relationships
pg_cast	casts (data type conversions)
pg_class	tables, indexes, sequences, views (“relations”)
pg_collation	collations (locale information)
pg_constraint	check constraints, unique constraints, primary key constraints, foreign key constraints
pg_conversion	encoding conversion information
pg_database	databases within this database cluster
pg_db_role_setting	per-role and per-database settings
pg_default_acl	default privileges for object types
pg_depend	dependencies between database objects
pg_description	descriptions or comments on database objects
pg_enum	enum label and value definitions
pg_event_trigger	event triggers
pg_extension	installed extensions
pg_foreign_data_wrapper	foreign-data wrapper definitions
pg_foreign_server	foreign server definitions
pg_foreign_table	additional foreign table information
pg_index	additional index information
pg_inherits	table inheritance hierarchy
pg_init_privs	object initial privileges
pg_language	languages for writing functions
pg_largeobject	data pages for large objects
pg_largeobject_metadata	metadata for large objects
pg_namespace	schemas
pg_opclass	access method operator classes
pg_operator	operators
pg_opfamily	access method operator families
pg_parameter_acl	configuration parameters for which privileges have been granted
pg_partitioned_table	information about partition key of tables
pg_policy	row-security policies
pg_proc	functions and procedures
pg_publication	publications for logical replication
pg_publication_namespace	schema to publication mapping
pg_publication_rel	relation to publication mapping
pg_range	information about range types
pg_replication_origin	registered replication origins
pg_rewrite	query rewrite rules
pg_seclabel	security labels on database objects
pg_sequence	information about sequences
pg_shdepend	dependencies on shared objects
pg_shdescription	comments on shared objects
pg_shseclabel	security labels on shared database objects
pg_statistic	planner statistics
pg_statistic_ext	extended planner statistics (definition)
pg_statistic_ext_data	extended planner statistics (built statistics)
pg_subscription	logical replication subscriptions
pg_subscription_rel	relation state for subscriptions
pg_tablespace	tablespaces within this database cluster
pg_transform	transforms (data type to procedural language conversions)
pg_trigger	triggers
pg_ts_config	text search configurations
pg_ts_config_map	text search configurations' token mappings
pg_ts_dict	text search dictionaries
pg_ts_parser	text search parsers
pg_ts_template	text search templates
pg_type	data types
pg_user_mapping	mappings of users to foreign servers

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pg_aggregate

The catalog pg_aggregate stores information about aggregate functions. An aggregate function is a function that operates on a set of values (typically one column from each row that matches a query condition) and returns a single value computed from all these values. Typical aggregate functions are sum, count, and max. Each entry in pg_aggregate is an extension of an entry in pg_proc. The pg_proc entry carries the aggregate's name, input and output data types, and other information that is similar to ordinary functions.

Table 2. pg_aggregate Columns

Column Type
	Description
aggfnoid regproc (references pg_proc.oid)
	pg_proc OID of the aggregate function
aggkind char
	Aggregate kind: n for “normal” aggregates, o for “ordered-set” aggregates, or h for “hypothetical-set” aggregates
aggnumdirectargs int2
	Number of direct (non-aggregated) arguments of an ordered-set or hypothetical-set aggregate, counting a variadic array as one argument. If equal to pronargs, the aggregate must be variadic and the variadic array describes the aggregated arguments as well as the final direct arguments. Always zero for normal aggregates.
aggtransfn regproc (references pg_proc.oid)
	Transition function
aggfinalfn regproc (references pg_proc.oid)
	Final function (zero if none)
aggcombinefn regproc (references pg_proc.oid)
	Combine function (zero if none)
aggserialfn regproc (references pg_proc.oid)
	Serialization function (zero if none)
aggdeserialfn regproc (references pg_proc.oid)
	Deserialization function (zero if none)
aggmtransfn regproc (references pg_proc.oid)
	Forward transition function for moving-aggregate mode (zero if none)
agminvtransfn regproc (references pg_proc.oid)
	Inverse transition function for moving-aggregate mode (zero if none)
aggmfinalfn regproc (references pg_proc.oid)
	Final function for moving-aggregate mode (zero if none)
aggfinalextra bool
	True to pass extra dummy arguments to aggfinalfn
aggmfinalextra bool
	True to pass extra dummy arguments to aggmfinalfn
aggfinalmodify char
	Whether aggfinalfn modifies the transition state value: r if it is read-only, s if the aggtransfn cannot be applied after the aggfinalfn, or w if it writes on the value
aggmfinalmodify char
	Like aggfinalmodify, but for the aggmfinalfn
aggsortop oid (references pg_operator.oid)
	Associated sort operator (zero if none)
aggtranstype oid (references pg_type.oid)
	Data type of the aggregate function's internal transition (state) data
aggtransspace int4
	Approximate average size (in bytes) of the transition state data, or zero to use a default estimate
aggmtranstype oid (references pg_type.oid)
	Data type of the aggregate function's internal transition (state) data for moving-aggregate mode (zero if none)
aggmtransspace int4
	Approximate average size (in bytes) of the transition state data for moving-aggregate mode, or zero to use a default estimate
agginitval text
	The initial value of the transition state. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null.
aggminitval text
	The initial value of the transition state for moving-aggregate mode. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null.

New aggregate functions are registered with the [CREATE AGGREGATE] command. See Section User-Defined Aggregates for more information about writing aggregate functions and the meaning of the transition functions, etc.

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pg_am

The catalog pg_am stores information about relation access methods. There is one row for each access method supported by the system. Currently, only tables and indexes have access methods. The requirements for table and index access methods are discussed in detail in Chapter Table Access Method Interface Definition and Chapter Index Access Method Interface Definition respectively.

Table 3. pg_am Columns

Column Type
	Description
oid oid
	Row identifier
amname name
	Name of the access method
amhandler regproc (references pg_proc.oid)
	OID of a handler function that is responsible for supplying information about the access method
amtype char
	t = table (including materialized views), i = index.

Note
All data about properties of index access methods is only directly visible at the C code level. However, pg_index_column_has_property() and related functions have been added to allow SQL queries to inspect index access method properties; see Table [Функции для получения информации из системных каталогов].

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pg_amop

The catalog pg_amop stores information about operators associated with access method operator families. There is one row for each operator that is a member of an operator family. A family member can be either a search operator or an ordering operator. An operator can appear in more than one family, but cannot appear in more than one search position nor more than one ordering position within a family. (It is allowed, though unlikely, for an operator to be used for both search and ordering purposes.)

Table 4. pg_amop Columns

Column Type
	Description
oid oid
	Row identifier
amopfamily oid (references pg_opfamily.oid)
	The operator family this entry is for
amoplefttype oid (references pg_type.oid)
	Left-hand input data type of operator/td>
amoprighttype oid (references pg_type.oid)
	Right-hand input data type of operator
amopstrategy int2
	Operator strategy number
amoppurpose char
	Operator purpose, either s for search or o for ordering
amopopr oid (references pg_operator.oid)
	OID of the operator
amopmethod oid (references pg_am.oid)
	Index access method operator family is for
amopsortfamily oid (references pg_opfamily.oid)
	The B-tree operator family this entry sorts according to, if an ordering operator; zero if a search operator

A “search” operator entry indicates that an index of this operator family can be searched to find all rows satisfying WHERE indexed_column operator constant. Obviously, such an operator must return boolean, and its left-hand input type must match the index's column data type.

An “ordering” operator entry indicates that an index of this operator family can be scanned to return rows in the order represented by ORDER BY indexed_column operator constant. Such an operator could return any sortable data type, though again its left-hand input type must match the index's column data type. The exact semantics of the ORDER BY are specified by the amopsortfamily column, which must reference a B-tree operator family for the operator's result type.

Note
At present, it's assumed that the sort order for an ordering operator is the default for the referenced operator family, i.e., ASC NULLS LAST. This might someday be relaxed by adding additional columns to specify sort options explicitly.

An entry's amopmethod must match the opfmethod of its containing operator family (including amopmethod here is an intentional denormalization of the catalog structure for performance reasons). Also, amoplefttype and amoprighttype must match the oprleft and oprright fields of the referenced pg_operator entry.

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pg_amproc

The catalog pg_amproc stores information about support functions associated with access method operator families. There is one row for each support function belonging to an operator family.

Table 5. pg_amproc Columns

Column Type
	Description
oid oid
	Row identifier
amprocfamily oid (references pg_opfamily.oid)
	The operator family this entry is for
amproclefttype oid (references pg_type.oid)
	Left-hand input data type of associated operator
amprocrighttype oid (references pg_type.oid)
	Right-hand input data type of associated operator
amprocnum int2
	Support function number
amproc regproc (references pg_proc.oid)
	OID of the function

The usual interpretation of the amproclefttype and amprocrighttype fields is that they identify the left and right input types of the operator(s) that a particular support function supports. For some access methods these match the input data type(s) of the support function itself, for others not. There is a notion of “default” support functions for an index, which are those with amproclefttype and amprocrighttype both equal to the index operator class's opcintype.

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pg_attrdef

The catalog pg_attrdef stores column default values. The main information about columns is stored in pg_attribute. Only columns for which a default value has been explicitly set will have an entry here.

Table 6. pg_attrdef Columns

Column Type
	Description
oid oid
	Row identifier
adrelid oid (references pg_class.oid)
	The table this column belongs to
adnum int2 (references pg_attribute.attnum)
	The number of the column
adbin pg_node_tree
	The column default value, in nodeToString() representation. Use pg_get_expr(adbin, adrelid) to convert it to an SQL expression.

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pg_attribute

The catalog pg_attribute stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. (There will also be attribute entries for indexes, and indeed all objects that have pg_class entries.)

The term attribute is equivalent to column and is used for historical reasons.

Table 7. pg_attribute Columns

Column Type
	Description
attrelid oid (references pg_class.oid)
	The table this column belongs to
attname name
	The column name
atttypid oid (references pg_type.oid)
	The data type of this column (zero for a dropped column)
attstattarget int4
	attstattarget controls the level of detail of statistics accumulated for this column by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of “most common values” to collect, and the target number of histogram bins to create.
attlen int2
	A copy of pg_type.typlen of this column's type
attnum int2
	The number of the column. Ordinary columns are numbered from 1 up. System columns, such as ctid, have (arbitrary) negative numbers.
attndims int4
	Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means “it's an array”.)
attcacheof int4
	Always -1 in storage, but when loaded into a row descriptor in memory this might be updated to cache the offset of the attribute within the row
atttypmod int4
	atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod.
attbyval bool
	A copy of pg_type.typbyval of this column's type
attalign char
	A copy of pg_type.typalign of this column's type
attstorage char
	Normally a copy of pg_type.typstorage of this column's type. For TOAST-able data types, this can be altered after column creation to control storage policy.
attcompression char
	The current compression method of the column. Typically this is '\0' to specify use of the current default setting (see default_toast_compression). Otherwise, 'p' selects pglz compression, while 'l' selects LZ4 compression. However, this field is ignored whenever attstorage does not allow compression.
attnotnull bool
	This represents a not-null constraint.
atthasdef bool
	This column has a default expression or generation expression, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the expression. (Check attgenerated to determine whether this is a default or a generation expression.)
atthasmissing bool
	This column has a value which is used where the column is entirely missing from the row, as happens when a column is added with a non-volatile DEFAULT value after the row is created. The actual value used is stored in the attmissingval column.
attidentity char
	If a zero byte (''), then not an identity column. Otherwise, a = generated always, d = generated by default.
attgenerated char
	If a zero byte (''), then not a generated column. Otherwise, s = stored. (Other values might be added in the future.)
attisdropped bool
	This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL.
attislocal bool
	This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously.
attinhcount int4
	The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed.
attcollation oid (references pg_collation.oid)
	The defined collation of the column, or zero if the column is not of a collatable data type
attacl aclitem[]
	Column-level access privileges, if any have been granted specifically on this column
attoptions text[]
	Attribute-level options, as “keyword=value” strings
attfdwoptions text[]
	Attribute-level foreign data wrapper options, as “keyword=value” strings
attmissingval anyarray
	This column has a one element array containing the value used when the column is entirely missing from the row, as happens when the column is added with a non-volatile DEFAULT value after the row is created. The value is only used when atthasmissing is true. If there is no value the column is null.

In a dropped column's pg_attribute entry, atttypid is reset to zero, but attlen and the other fields copied from pg_type are still valid. This arrangement is needed to cope with the situation where the dropped column's data type was later dropped, and so there is no pg_type row anymore. attlen and the other fields can be used to interpret the contents of a row of the table.

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pg_authid

The catalog pg_authid contains information about database authorization identifiers (roles). A role subsumes the concepts of “users” and “groups”. A user is essentially just a role with the rolcanlogin flag set. Any role (with or without rolcanlogin) can have other roles as members; see pg_auth_members.

Since this catalog contains passwords, it must not be publicly readable. pg_roles is a publicly readable view on pg_authid that blanks out the password field.

Chapter Database Roles contains detailed information about user and privilege management.

Because user identities are cluster-wide, pg_authid is shared across all databases of a cluster: there is only one copy of pg_authid per cluster, not one per database.

Table 8. pg_authid Columns

Column Type
	Description
oid oid
	Row identifier
rolname name
	Role name
rolsuper bool
	Role has superuser privileges
rolinherit bool
	Role automatically inherits privileges of roles it is a member of
rolcreaterole bool
	Role can create more roles
rolcreatedb bool
	Role can create databases
rolcanlogin bool
	Role can log in. That is, this role can be given as the initial session authorization identifier.
rolreplication bool
	Role is a replication role. A replication role can initiate replication connections and create and drop replication slots.
rolbypassrls bool
	Role bypasses every row-level security policy, see Section Row Security Policies for more information.
rolconnlimit int4
	For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit.
rolpassword text
	Password (possibly encrypted); null if none. The format depends on the form of encryption used.
rolvaliduntil timestamptz
	Password expiry time (only used for password authentication); null if no expiration

For an MD5 encrypted password, rolpassword column will begin with the string md5 followed by a 32-character hexadecimal MD5 hash. The MD5 hash will be of the user's password concatenated to their user name. For example, if user joe has password xyzzy, QHB will store the md5 hash of xyzzyjoe.

If the password is encrypted with SCRAM-SHA-256, it has the format:

SCRAM-SHA-256$<iteration count>:<salt>$<StoredKey>:<ServerKey>

where salt, StoredKey and ServerKey are in Base64 encoded format. This format is the same as that specified by RFC 5803.

A password that does not follow either of those formats is assumed to be unencrypted.

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pg_auth_members

The catalog pg_auth_members shows the membership relations between roles. Any non-circular set of relationships is allowed.

Because user identities are cluster-wide, pg_auth_members is shared across all databases of a cluster: there is only one copy of pg_auth_members per cluster, not one per database.

Table 9. pg_auth_members Columns

Column Type
	Description
roleid oid (references pg_authid.oid)
	ID of a role that has a member
member oid (references pg_authid.oid)
	ID of a role that is a member of roleid
grantor oid (references pg_authid.oid)
	ID of the role that granted this membership
admin_option bool
	True if member can grant membership in roleid to others

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pg_cast

The catalog pg_cast stores data type conversion paths, both built-in and user-defined.

It should be noted that pg_cast does not represent every type conversion that the system knows how to perform; only those that cannot be deduced from some generic rule. For example, casting between a domain and its base type is not explicitly represented in pg_cast. Another important exception is that “automatic I/O conversion casts”, those performed using a data type's own I/O functions to convert to or from text or other string types, are not explicitly represented in pg_cast.

Table 10. pg_cast Columns

Column Type
	Description
oid oid
	Row identifier
castsource oid (references pg_type.oid)
	OID of the source data type
casttarget oid (references pg_type.oid)
	OID of the target data type
castfunc oid (references pg_proc.oid)
	The OID of the function to use to perform this cast. Zero is stored if the cast method doesn't require a function.
castcontext char
	Indicates what contexts the cast can be invoked in. e means only as an explicit cast (using CAST or :: syntax). a means implicitly in assignment to a target column, as well as explicitly. i means implicitly in expressions, as well as the other cases.
castmethod char
	Indicates how the cast is performed. f means that the function specified in the castfunc field is used. i means that the input/output functions are used. b means that the types are binary-coercible, thus no conversion is required.

The cast functions listed in pg_cast must always take the cast source type as their first argument type, and return the cast destination type as their result type. A cast function can have up to three arguments. The second argument, if present, must be type integer; it receives the type modifier associated with the destination type, or -1 if there is none. The third argument, if present, must be type boolean; it receives true if the cast is an explicit cast, false otherwise.

It is legitimate to create a pg_cast entry in which the source and target types are the same, if the associated function takes more than one argument. Such entries represent “length coercion functions” that coerce values of the type to be legal for a particular type modifier value.

When a pg_cast entry has different source and target types and a function that takes more than one argument, it represents converting from one type to another and applying a length coercion in a single step. When no such entry is available, coercion to a type that uses a type modifier involves two steps, one to convert between data types and a second to apply the modifier.

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pg_class

The catalog pg_class describes tables and other objects that have columns or are otherwise similar to a table. This includes indexes (but see also pg_index), sequences (but see also pg_sequence), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all of pg_class's columns are meaningful for all relation kinds.

Table 11. pg_class Columns

Column Type
	Description
oid oid
	Row identifier
relname name
	Name of the table, index, view, etc.
relnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this relation
reltype oid (references pg_type.oid)
	The OID of the data type that corresponds to this table's row type, if any; zero for indexes, sequences, and toast tables, which have no pg_type entry
reloftype oid (references pg_type.oid)
	For typed tables, the OID of the underlying composite type; zero for all other relations
relowner oid (references pg_authid.oid)
	Owner of the relation
relam oid (references pg_am.oid)
	If this is a table or an index, the access method used (heap, B-tree, hash, etc.); otherwise zero (zero occurs for sequences, as well as relations without storage, such as views)
relfilenode oid
	Name of the on-disk file of this relation; zero means this is a “mapped” relation whose disk file name is determined by low-level state
reltablespace oid (references pg_tablespace.oid)
	The tablespace in which this relation is stored. If zero, the database's default tablespace is implied. (Not meaningful if the relation has no on-disk file.)
relpages int4
	Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
reltuples float4
	Number of live rows in the table. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. If the table has never yet been vacuumed or analyzed, reltuples contains -1 indicating that the row count is unknown.
relallvisible int4
	Number of pages that are marked all-visible in the table's visibility map. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
reltoastrelid oid (references pg_class.oid)
	OID of the TOAST table associated with this table, zero if none. The TOAST table stores large attributes “out of line” in a secondary table.
relhasindex bool
	True if this is a table and it has (or recently had) any indexes
relisshared bool
	True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared.
relpersistence char
	p = permanent table/sequence, u = unlogged table/sequence, t = temporary table/sequence
relkind char
	r = ordinary table, i = index, S = sequence, t = TOAST table, v = view, m = materialized view, c = composite type, f = foreign table, p = partitioned table, I = partitioned index
relnatts int2
	Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute. See also pg_attribute.attnum.
relchecks int2
	Number of CHECK constraints on the table; see pg_constraint catalog
relhasrules bool
	True if table has (or once had) rules; see pg_rewrite catalog
relhastriggers bool
	True if table has (or once had) triggers; see pg_trigger catalog
relhassubclass bool
	True if table or index has (or once had) any inheritance children or partitions
relrowsecurity bool
	True if table has row-level security enabled; see pg_policy catalog
relforcerowsecurity bool
	True if row-level security (when enabled) will also apply to table owner; see pg_policy catalog
relispopulated bool
	True if relation is populated (this is true for all relations other than some materialized views)
relreplident char
	Columns used to form “replica identity” for rows: d = default (primary key, if any), n = nothing, f = all columns, i = index with indisreplident set (same as nothing if the index used has been dropped)
relispartition bool
	True if table or index is a partition
relrewrite oid (references pg_class.oid)
	For new relations being written during a DDL operation that requires a table rewrite, this contains the OID of the original relation; otherwise zero. That state is only visible internally; this field should never contain anything other than zero for a user-visible relation.
relfrozenxid xid
	All transaction IDs before this one have been replaced with a permanent (“frozen”) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. Zero (InvalidTransactionId) if the relation is not a table.
relminmxid xid
	All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. Zero (InvalidMultiXactId) if the relation is not a table.
relacl aclitem[]
	Access privileges; see Section Privileges for details
reloptions text[]
	Access-method-specific options, as “keyword=value” strings
relpartbound pg_node_tree
	If table is a partition (see relispartition), internal representation of the partition bound

Several of the Boolean flags in pg_class are maintained lazily: they are guaranteed to be true if that's the correct state, but may not be reset to false immediately when the condition is no longer true. For example, relhasindex is set by [CREATE INDEX], but it is never cleared by [DROP INDEX]. Instead, [VACUUM], clears relhasindex if it finds the table has no indexes. This arrangement avoids race conditions and improves concurrency.

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pg_collation

The catalog pg_collation describes the available collations, which are essentially mappings from an SQL name to operating system locale categories. See Section Collation Support for more information.

Table 12. pg_collation Columns

Column Type
	Description
oid oid
	Row identifier
collname name
	Collation name (unique per namespace and encoding)
collnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this collation
collowner oid (references pg_authid.oid)
	Owner of the collation
collprovider char
	Provider of the collation: d = database default, c = libc, i = icu
collisdeterministic bool
	Is the collation deterministic?
collencoding int4
	Encoding in which the collation is applicable, or -1 if it works for any encoding
collcollate text
	LC_COLLATE for this collation object
collctype text
	LC_CTYPE for this collation object
colliculocale text
	ICU locale ID for this collation object
collversion text
	Provider-specific version of the collation. This is recorded when the collation is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.

Note that the unique key on this catalog is (collname, collencoding, collnamespace) not just (collname, collnamespace). QHB generally ignores all collations that do not have collencoding equal to either the current database's encoding or -1, and creation of new entries with the same name as an entry with collencoding = -1 is forbidden. Therefore it is sufficient to use a qualified SQL name (schema.name) to identify a collation, even though this is not unique according to the catalog definition. The reason for defining the catalog this way is that qhb_bootstrap (or initdb) fills it in at cluster initialization time with entries for all locales available on the system, so it must be able to hold entries for all encodings that might ever be used in the cluster.

In the template0 database, it could be useful to create collations whose encoding does not match the database encoding, since they could match the encodings of databases later cloned from template0. This would currently have to be done manually.

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pg_constraint

The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the pg_attribute catalog, not here.

User-defined constraint triggers (created with [CREATE CONSTRAINT TRIGGER]) also give rise to an entry in this table.

Check constraints on domains are stored here, too.

Table 13. pg_constraint Columns

Column Type
	Description
oid oid
	Row identifier
conname name
	Constraint name (not necessarily unique!)
connamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this constraint
contype char
	c = check constraint, f = foreign key constraint, p = primary key constraint, u = unique constraint, t = constraint trigger, x = exclusion constraint
condeferrable bool
	Is the constraint deferrable?
condeferred bool
	Is the constraint deferred by default?
convalidated bool
	Has the constraint been validated? Currently, can be false only for foreign keys and CHECK constraints
conrelid oid (references pg_class.oid)
	The table this constraint is on; zero if not a table constraint
contypid oid (references pg_type.oid)
	The domain this constraint is on; zero if not a domain constraint
conindid oid (references pg_class.oid)
	The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else zero
conparentid oid (references pg_constraint.oid)
	The corresponding constraint of the parent partitioned table, if this is a constraint on a partition; else zero
confrelid oid (references pg_class.oid)
	If a foreign key, the referenced table; else zero
confupdtype char
	Foreign key update action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confdeltype char
	Foreign key deletion action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confmatchtype char
	Foreign key match type: f = full, p = partial, s = simple
conislocal bool
	This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously.
coninhcount int4
	The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed.
connoinherit bool
	This constraint is defined locally for the relation. It is a non-inheritable constraint.
conkey int2[] (references pg_attribute.attnum)
	If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns
confkey int2[] (references pg_attribute.attnum)
	If a foreign key, list of the referenced columns
conpfeqop oid[] (references pg_operator.oid)
	If a foreign key, list of the equality operators for PK = FK comparisons
conppeqop oid[] (references pg_operator.oid)
	If a foreign key, list of the equality operators for PK = PK comparisons
conffeqop oid[] (references pg_operator.oid)
	If a foreign key, list of the equality operators for FK = FK comparisons
confdelsetcols int2[] (references pg_attribute.attnum)
	If a foreign key with a SET NULL or SET DEFAULT delete action, the columns that will be updated. If null, all of the referencing columns will be updated.
conexclop oid[] (references pg_operator.oid)
	If an exclusion constraint, list of the per-column exclusion operators
conbin pg_node_tree
	If a check constraint, an internal representation of the expression. (It's recommended to use pg_get_constraintdef() to extract the definition of a check constraint.)

In the case of an exclusion constraint, conkey is only useful for constraint elements that are simple column references. For other cases, a zero appears in conkey and the associated index must be consulted to discover the expression that is constrained. (conkey thus has the same contents as pg_index.indkey for the index.)

Note
pg_class.relchecks needs to agree with the number of check-constraint entries found in this table for each relation.

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pg_conversion

The catalog pg_conversion describes encoding conversion functions. See [CREATE CONVERSION] for more information.

Table 14. pg_conversion Columns

Column Type
	Description
oid oid
	Row identifier
conname name
	Conversion name (unique within a namespace)
connamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this conversion
conowner oid (references pg_authid.oid)
	Owner of the conversion
conforencoding int4
	Source encoding ID (pg_encoding_to_char() can translate this number to the encoding name)
contoencoding int4
	Destination encoding ID (pg_encoding_to_char() can translate this number to the encoding name)
conproc regproc (references pg_proc.oid)
	Conversion function
condefault bool
	True if this is the default conversion

---

---

pg_database

The catalog pg_database stores information about the available databases. Databases are created with the [CREATE DATABASE] command. Consult Chapter Managing Databases for details about the meaning of some of the parameters.

Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database.

Table 15. pg_database Columns

Column Type
	Description
oid oid
	Row identifier
datname name
	Database name
datdba oid (references pg_authid.oid)
	Owner of the database, usually the user who created it
encoding int4
	Character encoding for this database (pg_encoding_to_char() can translate this number to the encoding name)
datlocprovider char
	Locale provider for this database: c = libc, i = icu
datistemplate bool
	If true, then this database can be cloned by any user with CREATEDB privileges; if false, then only superusers or the owner of the database can clone it.
datallowconn bool
	If false then no one can connect to this database. This is used to protect the template0 database from being altered.
datconnlimit int4
	Sets maximum number of concurrent connections that can be made to this database. -1 means no limit, -2 indicates the database is invalid.
datfrozenxid xid
	All transaction IDs before this one have been replaced with a permanent (“frozen”) transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. It is the minimum of the per-table pg_class.relfrozenxid values.
datminmxid xid
	All multixact IDs before this one have been replaced with a transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. It is the minimum of the per-table pg_class.relminmxid values.
dattablespace oid (references pg_tablespace.oid)
	The default tablespace for the database. Within this database, all tables for which pg_class.reltablespace is zero will be stored in this tablespace; in particular, all the non-shared system catalogs will be there.
datcollate text
	LC_COLLATE for this database
datctype text
	LC_CTYPE for this database
daticulocale text
	ICU locale ID for this database
datcollversion text
	Provider-specific version of the collation. This is recorded when the database is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.
datacl aclitem[]
	Access privileges; see Section Privileges for details

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pg_db_role_setting

The catalog pg_db_role_setting records the default values that have been set for run-time configuration variables, for each role and database combination.

Unlike most system catalogs, pg_db_role_setting is shared across all databases of a cluster: there is only one copy of pg_db_role_setting per cluster, not one per database.

Table 16. pg_db_role_setting Columns

Column Type
	Description
setdatabase oid (references pg_database.oid)
	The OID of the database the setting is applicable to, or zero if not database-specific
setrole oid (references pg_authid.oid)
	The OID of the role the setting is applicable to, or zero if not role-specific
setconfig text[]
	Defaults for run-time configuration variables

---

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pg_default_acl

The catalog pg_default_acl stores initial privileges to be assigned to newly created objects.

Table 17. pg_default_acl Columns

Column Type
	Description
oid oid
	Row identifier
defaclrole oid (references pg_authid.oid)
	The OID of the role associated with this entry
defaclnamespace oid (references pg_namespace.oid)
	The OID of the namespace associated with this entry, or zero if none
defaclobjtype char
	Type of object this entry is for: r = relation (table, view), S = sequence, f = function, T = type, n = schema
defaclacl aclitem[]
	Access privileges that this type of object should have on creation

A pg_default_acl entry shows the initial privileges to be assigned to an object belonging to the indicated user. There are currently two types of entry: “global” entries with defaclnamespace = zero, and “per-schema” entries that reference a particular schema. If a global entry is present then it overrides the normal hard-wired default privileges for the object type. A per-schema entry, if present, represents privileges to be added to the global or hard-wired default privileges.

Note that when an ACL entry in another catalog is null, it is taken to represent the hard-wired default privileges for its object, not whatever might be in pg_default_acl at the moment. pg_default_acl is only consulted during object creation.

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pg_depend

The catalog pg_depend records the dependency relationships between database objects. This information allows DROP commands to find which other objects must be dropped by DROP CASCADE or prevent dropping in the DROP RESTRICT case.

See also pg_shdepend, which performs a similar function for dependencies involving objects that are shared across a database cluster.

Table 18. pg_depend Columns

Column Type
	Description
classid oid (references pg_class.oid)
	The OID of the system catalog the dependent object is in
objid oid (references any OID column)
	The OID of the specific dependent object
objsubid int4
	For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero.
refclassid oid (references pg_class.oid)
	The OID of the system catalog the referenced object is in
refobjid oid (references any OID column)
	The OID of the specific referenced object
refobjsubid int4
	For a table column, this is the column number (the refobjid and refclassid refer to the table itself). For all other object types, this column is zero.
deptype char
	A code defining the specific semantics of this dependency relationship; see text

In all cases, a pg_depend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype:

DEPENDENCY_NORMAL (n)
A normal relationship between separately-created objects. The dependent object can be dropped without affecting the referenced object. The referenced object can only be dropped by specifying CASCADE, in which case the dependent object is dropped, too. Example: a table column has a normal dependency on its data type.

DEPENDENCY_AUTO (a)
The dependent object can be dropped separately from the referenced object, and should be automatically dropped (regardless of RESTRICT or CASCADE mode) if the referenced object is dropped. Example: a named constraint on a table is made auto-dependent on the table, so that it will go away if the table is dropped.

DEPENDENCY_INTERNAL (i)
The dependent object was created as part of creation of the referenced object, and is really just a part of its internal implementation. A direct DROP of the dependent object will be disallowed outright (we'll tell the user to issue a DROP against the referenced object, instead). A DROP of the referenced object will result in automatically dropping the dependent object whether CASCADE is specified or not. If the dependent object has to be dropped due to a dependency on some other object being removed, its drop is converted to a drop of the referenced object, so that NORMAL and AUTO dependencies of the dependent object behave much like they were dependencies of the referenced object. Example: a view's ON SELECT rule is made internally dependent on the view, preventing it from being dropped while the view remains. Dependencies of the rule (such as tables it refers to) act as if they were dependencies of the view.

DEPENDENCY_PARTITION_PRI (P)
DEPENDENCY_PARTITION_SEC (S)
The dependent object was created as part of creation of the referenced object, and is really just a part of its internal implementation; however, unlike INTERNAL, there is more than one such referenced object. The dependent object must not be dropped unless at least one of these referenced objects is dropped; if any one is, the dependent object should be dropped whether or not CASCADE is specified. Also unlike INTERNAL, a drop of some other object that the dependent object depends on does not result in automatic deletion of any partition-referenced object. Hence, if the drop does not cascade to at least one of these objects via some other path, it will be refused. (In most cases, the dependent object shares all its non-partition dependencies with at least one partition-referenced object, so that this restriction does not result in blocking any cascaded delete.) Primary and secondary partition dependencies behave identically except that the primary dependency is preferred for use in error messages; hence, a partition-dependent object should have one primary partition dependency and one or more secondary partition dependencies. Note that partition dependencies are made in addition to, not instead of, any dependencies the object would normally have. This simplifies ATTACH/DETACH PARTITION operations: the partition dependencies need only be added or removed. Example: a child partitioned index is made partition-dependent on both the partition table it is on and the parent partitioned index, so that it goes away if either of those is dropped, but not otherwise. The dependency on the parent index is primary, so that if the user tries to drop the child partitioned index, the error message will suggest dropping the parent index instead (not the table).

DEPENDENCY_EXTENSION (е)
The dependent object is a member of the extension that is the referenced object (see pg_extension). The dependent object can be dropped only via [DROP EXTENSION] on the referenced object. Functionally this dependency type acts the same as an INTERNAL dependency, but it's kept separate for clarity and to simplify qhb_dump.

DEPENDENCY_AUTO_EXTENSION (x)
The dependent object is not a member of the extension that is the referenced object (and so it should not be ignored by qhb_dump), but it cannot function without the extension and should be auto-dropped if the extension is. The dependent object may be dropped on its own as well. Functionally this dependency type acts the same as an AUTO dependency, but it's kept separate for clarity and to simplify qhb_dump.

Other dependency flavors might be needed in future.

Note that it's quite possible for two objects to be linked by more than one pg_depend entry. For example, a child partitioned index would have both a partition-type dependency on its associated partition table, and an auto dependency on each column of that table that it indexes. This sort of situation expresses the union of multiple dependency semantics. A dependent object can be dropped without CASCADE if any of its dependencies satisfies its condition for automatic dropping. Conversely, all the dependencies' restrictions about which objects must be dropped together must be satisfied.

Most objects created during qhb_bootstrap (or initdb) are considered “pinned”, which means that the system itself depends on them. Therefore, they are never allowed to be dropped. Also, knowing that pinned objects will not be dropped, the dependency mechanism doesn't bother to make pg_depend entries showing dependencies on them. Thus, for example, a table column of type numeric notionally has a NORMAL dependency on the numeric data type, but no such entry actually appears in pg_depend.

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pg_description

The catalog pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the [COMMENT] command and viewed with psql's \d commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description.

See also pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a database cluster.

Table 19. pg_description Columns

Column Type
	Description
objoid oid (references any OID column)
	The OID of the object this description pertains to
classoid oid (references pg_class.oid)
	The OID of the system catalog this object appears in
objsubid int4
	For a comment on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
description text
	Arbitrary text that serves as the description of this object

---

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pg_enum

The pg_enum catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in pg_enum.

Table 20. pg_enum Columns

Column Type
	Description
oid oid
	Row identifier
enumtypid oid (references pg_type.oid)
	The OID of the pg_type entry owning this enum value
enumsortorder float4
	The sort position of this enum value within its enum type
enumlabel name
	The textual label for this enum value

The OIDs for pg_enum rows follow a special rule: even-numbered OIDs are guaranteed to be ordered in the same way as the sort ordering of their enum type. That is, if two even OIDs belong to the same enum type, the smaller OID must have the smaller enumsortorder value. Odd-numbered OID values need bear no relationship to the sort order. This rule allows the enum comparison routines to avoid catalog lookups in many common cases. The routines that create and alter enum types attempt to assign even OIDs to enum values whenever possible.

When an enum type is created, its members are assigned sort-order positions 1..n. But members added later might be given negative or fractional values of enumsortorder. The only requirement on these values is that they be correctly ordered and unique within each enum type.

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pg_event_trigger

The catalog pg_event_trigger stores event triggers. See Chapter Event Triggers for more information.

Table 21. pg_event_trigger Columns

Column Type
	Description
oid oid
	Row identifier
evtname name
	Trigger name (must be unique)
evtevent name
	Identifies the event for which this trigger fires
evtowner oid (references pg_authid.oid)
	Owner of the event trigger
evtfoid oid (references pg_proc.oid)
	The function to be called
evtenabled char
	Controls in which session_replication_role modes the event trigger fires. O = trigger fires in “origin” and “local” modes, D = trigger is disabled, R = trigger fires in “replica” mode, A = trigger fires always.
evttags text[]
	Command tags for which this trigger will fire. If NULL, the firing of this trigger is not restricted on the basis of the command tag.

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pg_extension

The catalog pg_extension stores information about the installed extensions. See Section Packaging Related Objects into an Extension for details about extensions.

Table 22. pg_extension Columns

Column Type
	Description
oid oid
	Row identifier
extname name
	Name of the extension
extowner oid (references pg_authid.oid)
	Owner of the extension
extnamespace oid (references pg_namespace.oid)
	Schema containing the extension's exported objects
extrelocatable bool
	True if extension can be relocated to another schema
extversion text
	Version name for the extension
extconfig oid[] (references pg_class.oid)
	Array of regclass OIDs for the extension's configuration table(s), or NULL if none
extcondition text[]
	Array of WHERE-clause filter conditions for the extension's configuration table(s), or NULL if none

Note that unlike most catalogs with a “namespace” column, extnamespace is not meant to imply that the extension belongs to that schema. Extension names are never schema-qualified. Rather, extnamespace indicates the schema that contains most or all of the extension's objects. If extrelocatable is true, then this schema must in fact contain all schema-qualifiable objects belonging to the extension.

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pg_foreign_data_wrapper

The catalog pg_foreign_data_wrapper stores foreign-data wrapper definitions. A foreign-data wrapper is the mechanism by which external data, residing on foreign servers, is accessed.

Table 23. pg_foreign_data_wrapper Columns

Column Type
	Description
oid oid
	Row identifier
fdwname name
	Name of the foreign-data wrapper
fdwowner oid (references pg_authid.oid)
	Owner of the foreign-data wrapper
fdwhandler oid (references pg_proc.oid)
	References a handler function that is responsible for supplying execution routines for the foreign-data wrapper. Zero if no handler is provided
fdwvalidator oid (references pg_proc.oid)
	References a validator function that is responsible for checking the validity of the options given to the foreign-data wrapper, as well as options for foreign servers and user mappings using the foreign-data wrapper. Zero if no validator is provided
fdwacl aclitem[]
	Access privileges; see Section Privileges for details
fdwoptions text[]
	Foreign-data wrapper specific options, as “keyword=value” strings

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pg_foreign_server

The catalog pg_foreign_server stores foreign server definitions. A foreign server describes a source of external data, such as a remote server. Foreign servers are accessed via foreign-data wrappers.

Table 24. pg_foreign_server Columns

Column Type
	Description
oid oid
	Row identifier
srvname name
	Name of the foreign server
srvowner oid (references pg_authid.oid)
	Owner of the foreign server
srvfdw oid (references pg_foreign_data_wrapper.oid)
	OID of the foreign-data wrapper of this foreign server
srvtype text
	Type of the server (optional)
srvversion text
	Version of the server (optional)
srvacl aclitem[]
	Access privileges; see Section Privileges for details
srvoptions text[]
	Foreign server specific options, as “keyword=value” strings

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pg_foreign_table

The catalog pg_foreign_table contains auxiliary information about foreign tables. A foreign table is primarily represented by a pg_class entry, just like a regular table. Its pg_foreign_table entry contains the information that is pertinent only to foreign tables and not any other kind of relation.

Table 25. pg_foreign_table Columns

Column Type
	Description
ftrelid oid (references pg_class.oid)
	The OID of the pg_class entry for this foreign table
ftserver oid (references pg_foreign_server.oid)
	OID of the foreign server for this foreign table
ftoptions text[]
	Foreign table options, as “keyword=value” strings

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pg_index

The catalog pg_index contains part of the information about indexes. The rest is mostly in pg_class.

Table 26. pg_index Columns

Column Type
	Description
indexrelid oid (references pg_class.oid)
	The OID of the pg_class entry for this index
indrelid oid (references pg_class.oid)
	The OID of the pg_class entry for the table this index is for
indnatts int2
	The total number of columns in the index (duplicates pg_class.relnatts); this number includes both key and included attributes
indnkeyatts int2
	The number of key columns in the index, not counting any included columns, which are merely stored and do not participate in the index semantics
indisunique bool
	If true, this is a unique index
indnullsnotdistinct bool
	This value is only used for unique indexes. If false, this unique index will consider null values distinct (so the index can contain multiple null values in a column, the default QHB behavior). If it is true, it will consider null values to be equal (so the index can only contain one null value in a column).
indisprimary bool
	If true, this index represents the primary key of the table (indisunique should always be true when this is true)
indisexclusion bool
	If true, this index supports an exclusion constraint
indimmediate bool
	If true, the uniqueness check is enforced immediately on insertion (irrelevant if indisunique is not true)
indisclustered bool
	If true, the table was last clustered on this index
indisvalid bool
	If true, the index is currently valid for queries. False means the index is possibly incomplete: it must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is unique, the uniqueness property is not guaranteed true either.
indcheckxmin bool
	If true, queries must not use the index until the xmin of this pg_index row is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see
indisready bool
	If true, the index is currently ready for inserts. False means the index must be ignored by INSERT/UPDATE operations.
indislive bool
	If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions)
indisreplident bool
	If true this index has been chosen as “replica identity” using ALTER TABLE ... REPLICA IDENTITY USING INDEX ...
indkey int2vector (references pg_attribute.attnum)
	This is an array of indnatts values that indicate which table columns this index indexes. For example, a value of 1 3 would mean that the first and the third table columns make up the index entries. Key columns come before non-key (included) columns. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference.
indcollation oidvector (references pg_collation.oid)
	For each column in the index key (indnkeyatts values), this contains the OID of the collation to use for the index, or zero if the column is not of a collatable data type.
indclass oidvector (references pg_opclass.oid)
	For each column in the index key (indnkeyatts values), this contains the OID of the operator class to use. See pg_opclass for details.
indoption int2vector
	This is an array of indnkeyatts values that store per-column flag bits. The meaning of the bits is defined by the index's access method.
indexprs pg_node_tree
	Expression trees (in nodeToString() representation) for index attributes that are not simple column references. This is a list with one element for each zero entry in indkey. Null if all index attributes are simple references.
indpred pg_node_tree
	Expression tree (in nodeToString() representation) for partial index predicate. Null if not a partial index.

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pg_inherits

The catalog pg_inherits records information about table and index inheritance hierarchies. There is one entry for each direct parent-child table or index relationship in the database. (Indirect inheritance can be determined by following chains of entries.)

Table 27. pg_inherits Columns

Column Type
	Description
inhrelid oid (references pg_class.oid)
	The OID of the child table or index
inparent oid (references pg_class.oid)
	The OID of the parent table or index
inhseqno int4
	If there is more than one direct parent for a child table (multiple inheritance), this number tells the order in which the inherited columns are to be arranged. The count starts at 1. Indexes cannot have multiple inheritance, since they can only inherit when using declarative partitioning.
inhdetachpending bool
	true for a partition that is in the process of being detached; false otherwise.

---

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pg_init_privs

The catalog pg_init_privs records information about the initial privileges of objects in the system. There is one entry for each object in the database which has a non-default (non-NULL) initial set of privileges.

Objects can have initial privileges either by having those privileges set when the system is initialized (by qhb_bootstrap) or when the object is created during a [CREATE EXTENSION] and the extension script sets initial privileges using the [GRANT] system. Note that the system will automatically handle recording of the privileges during the extension script and that extension authors need only use the GRANT and REVOKE statements in their script to have the privileges recorded. The privtype column indicates if the initial privilege was set by qhb_bootstrap or during a CREATE EXTENSION command.

Objects which have initial privileges set by qhb_bootstrap will have entries where privtype is 'i', while objects which have initial privileges set by CREATE EXTENSION will have entries where privtype is 'e'.

Table 28. pg_init_privs Columns

Column Type
	Description
objoid oid (references any OID column)
	The OID of the specific object
classoid oid (references pg_class.oid)
	The OID of the system catalog the object is in
objsubid int4
	For a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
privtype char
	A code defining the type of initial privilege of this object; see text
initprivs aclitem[]
	The initial access privileges; see Section Privileges for details

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pg_language

The catalog pg_language registers languages in which you can write functions or stored procedures. See [CREATE LANGUAGE] and Chapter Procedural Languages for more information about language handlers.

Table 29. pg_language Columns

Column Type
	Description
oid oid
	Row identifier
lanname name
	Name of the language
lanowner oid (references pg_authid.oid)
	Owner of the language
lanispl bool
	This is false for internal languages (such as SQL) and true for user-defined languages. Currently, qhb_dump still uses this to determine which languages need to be dumped, but this might be replaced by a different mechanism in the future.
lanplusted bool
	True if this is a trusted language, which means that it is believed not to grant access to anything outside the normal SQL execution environment. Only superusers can create functions in untrusted languages.
lanplcallfoid oid (references pg_proc.oid)
	For noninternal languages this references the language handler, which is a special function that is responsible for executing all functions that are written in the particular language. Zero for internal languages.
laninline oid (references pg_proc.oid)
	This references a function that is responsible for executing “inline” anonymous code blocks (DO blocks). Zero if inline blocks are not supported.
lanvalidator oid (references pg_proc.oid)
	This references a language validator function that is responsible for checking the syntax and validity of new functions when they are created. Zero if no validator is provided.
lanacl aclitem[]
	Access privileges; see Section Privileges for details

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pg_largeobject

The catalog pg_largeobject holds the data making up “large objects”. A large object is identified by an OID assigned when it is created. Each large object is broken into segments or “pages” small enough to be conveniently stored as rows in pg_largeobject. The amount of data per page is defined to be LOBLKSIZE (which is currently BLCKSZ/4, or typically 2 kB).

Use pg_largeobject_metadata to obtain a list of large object OIDs.

Table 30. pg_largeobject Columns

Column Type
	Description
loid oid (references pg_largeobject_metadata.oid)
	Identifier of the large object that includes this page
pageno int4
	Page number of this page within its large object (counting from zero)
data bytea
	Actual data stored in the large object. This will never be more than LOBLKSIZE bytes and might be less.

Each row of pg_largeobject holds data for one page of a large object, beginning at byte offset (pageno * LOBLKSIZE) within the object. The implementation allows sparse storage: pages might be missing, and might be shorter than LOBLKSIZE bytes even if they are not the last page of the object. Missing regions within a large object read as zeroes.

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---

pg_largeobject_metadata

The catalog pg_largeobject_metadata holds metadata associated with large objects. The actual large object data is stored in pg_largeobject.

Table 31. pg_largeobject_metadata Columns

Column Type
	Description
oid oid
	Row identifier
lomowner oid (references pg_authid.oid)
	Owner of the large object
lomacl aclitem[]
	Access privileges; see Section Privileges for details

---

---

pg_namespace

The catalog pg_namespace stores namespaces. A namespace is the structure underlying SQL schemas: each namespace can have a separate collection of relations, types, etc. without name conflicts.

Table 32. pg_namespace Columns

Column Type
	Description
oid oid
	Row identifier
nspname name
	Name of the namespace
nspowner oid (references pg_authid.oid)
	Owner of the namespace
nspacl aclitem[]
	Access privileges; see Section Privileges for details

---

---

pg_opclass

The catalog pg_opclass defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input.

Operator classes are described at length in Section Interfacing Extensions to Indexes.

Table 33. pg_opclass Columns

Column Type
	Description
oid oid
	Row identifier
opcmethod oid (references pg_am.oid)
	Index access method operator class is for
opcname name
	Name of this operator class
opcnamespace oid (references pg_namespace.oid)
	Namespace of this operator class
opcowner oid (references pg_authid.oid)
	Owner of the operator class
opcfamily oid (references pg_opfamily.oid)
	Operator family containing the operator class
opcintype oid (references pg_type.oid)
	Data type that the operator class indexes
opcdefault bool
	True if this operator class is the default for opcintype
opckeytype oid (references pg_type.oid)
	Type of data stored in index, or zero if same as opcintype

An operator class's opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype.

---

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pg_operator

The catalog pg_operator stores information about operators. See [CREATE OPERATOR] and Section User-Defined Operators for more information.

Table 34. pg_operator Columns

Column Type
	Description
oid oid
	Row identifier
oprname name
	Name of the operator
oprnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this operator
oprowner oid (references pg_authid.oid)
	Owner of the operator
oprkind char
	b = infix operator (“both”), or l = prefix operator (“left”)
oprcanmerge bool
	This operator supports merge joins
oprcanhash bool
	This operator supports hash joins
oprleft oid (references pg_type.oid)
	Type of the left operand (zero for a prefix operator)
oprright oid (references pg_type.oid)
	Type of the right operand
oprresult oid (references pg_type.oid)
	Type of the result (zero for a not-yet-defined “shell” operator)
oprcom oid (references pg_operator.oid)
	Commutator of this operator (zero if none)
oprnegate oid (references pg_operator.oid)
	Negator of this operator (zero if none)
oprcode regproc (references pg_proc.oid)
	Function that implements this operator (zero for a not-yet-defined “shell” operator)
oprrest regproc (references pg_proc.oid)
	Restriction selectivity estimation function for this operator (zero if none)
oprjoin regproc (references pg_proc.oid)
	Join selectivity estimation function for this operator (zero if none)

---

---

pg_opfamily

The catalog pg_opfamily defines operator families. Each operator family is a collection of operators and associated support routines that implement the semantics specified for a particular index access method. Furthermore, the operators in a family are all “compatible”, in a way that is specified by the access method. The operator family concept allows cross-data-type operators to be used with indexes and to be reasoned about using knowledge of access method semantics.

Operator families are described at length in Section Interfacing Extensions to Indexes.

Table 35. pg_opfamily Columns

Column Type
	Description
oid oid
	Row identifier
opfmethod oid (references pg_am.oid)
	Index access method operator family is for
opfname name
	Name of this operator family
opfnamespace oid (references pg_namespace.oid)
	Namespace of this operator family
opfowner oid (references pg_authid.oid)
	Owner of the operator family

The majority of the information defining an operator family is not in its pg_opfamily row, but in the associated rows in pg_amop, pg_amproc, and pg_opclass.

---

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pg_parameter_acl

The catalog pg_parameter_acl records configuration parameters for which privileges have been granted to one or more roles. No entry is made for parameters that have default privileges.

Unlike most system catalogs, pg_parameter_acl is shared across all databases of a cluster: there is only one copy of pg_parameter_acl per cluster, not one per database.

Table 36. pg_parameter_acl Columns

Column Type
	Description
oid oid
	Row identifier
parname text
	The name of a configuration parameter for which privileges are granted
paracl aclitem[]
	Access privileges; see Section Privileges for details

---

---

pg_partitioned_table

The catalog pg_partitioned_table stores information about how tables are partitioned.

Table 37. pg_partitioned_table Columns

Column Type
	Description
partrelid oid (references pg_class.oid)
	The OID of the pg_class entry for this partitioned table
partstrat char
	Partitioning strategy; h = hash partitioned table, l = list partitioned table, r = range partitioned table
partnatts int2
	The number of columns in the partition key
partdefid oid (references pg_class.oid)
	The OID of the pg_class entry for the default partition of this partitioned table, or zero if this partitioned table does not have a default partition
partattrs int2vector (references pg_attribute.attnum)
	This is an array of partnatts values that indicate which table columns are part of the partition key. For example, a value of 1 3 would mean that the first and the third table columns make up the partition key. A zero in this array indicates that the corresponding partition key column is an expression, rather than a simple column reference.
partclass oidvector (references pg_opclass.oid)
	For each column in the partition key, this contains the OID of the operator class to use. See pg_opclass for details.
partcollation oidvector (references pg_opclass.oid)
	For each column in the partition key, this contains the OID of the collation to use for partitioning, or zero if the column is not of a collatable data type.
partexprs pg_node_tree
	Expression trees (in nodeToString() representation) for partition key columns that are not simple column references. This is a list with one element for each zero entry in partattrs. Null if all partition key columns are simple references.

---

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pg_policy

The catalog pg_policy stores row-level security policies for tables. A policy includes the kind of command that it applies to (possibly all commands), the roles that it applies to, the expression to be added as a security-barrier qualification to queries that include the table, and the expression to be added as a WITH CHECK option for queries that attempt to add new records to the table.

Table 38. pg_policy Columns

Column Type
	Description
oid oid
	Row identifier
polname name
	The name of the policy
polrelid oid (references pg_class.oid)
	The table to which the policy applies
polcmd char
	The command type to which the policy is applied: r for SELECT, a for INSERT, w for UPDATE, d for DELETE, or * for all
polpermissive bool
	Is the policy permissive or restrictive?
polroles oid[] (references pg_authid.oid)
	The roles to which the policy is applied; zero means PUBLIC (and normally appears alone in the array)
polqual pg_node_tree
	The expression tree to be added to the security barrier qualifications for queries that use the table
polwithcheck pg_node_tree
	The expression tree to be added to the WITH CHECK qualifications for queries that attempt to add rows to the table

Note
Policies stored in pg_policy are applied only when pg_class. relrowsecurity is set for their table.

---

---

pg_proc

The catalog pg_proc stores information about functions, procedures, aggregate functions, and window functions (collectively also known as routines). See [CREATE FUNCTION], [CREATE PROCEDURE], and Section User-Defined Functions for more information.

If prokind indicates that the entry is for an aggregate function, there should be a matching row in pg_aggregate.

Table 39. pg_proc Columns

Column Type
	Description
oid oid
	Row identifier
proname name
	Name of the function
pronamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this function
proowner oid (references pg_authid.oid)
	Owner of the function
prolang oid (references pg_language.oid)
	Implementation language or call interface of this function
procost float4
	Estimated execution cost (in units of cpu_operator_cost); if proretset, this is cost per row returned
prorows float4
	Estimated number of result rows (zero if not proretset)
provariadic oid (references pg_type.oid)
	Data type of the variadic array parameter's elements, or zero if the function does not have a variadic parameter
prosupport regproc (references pg_proc.oid)
	Planner support function for this function (see Section Function Optimization Information), or zero if none
prokind char
	f for a normal function, p for a procedure, a for an aggregate function, or w for a window function
prosecdef bool
	Function is a security definer (i.e., a “setuid” function)
proleakproof bool
	The function has no side effects. No information about the arguments is conveyed except via the return value. Any function that might throw an error depending on the values of its arguments is not leak-proof.
proisstrict bool
	Function returns null if any call argument is null. In that case the function won't actually be called at all. Functions that are not “strict” must be prepared to handle null inputs.
proretset bool
	Function returns a set (i.e., multiple values of the specified data type)
provolatile char
	provolatile tells whether the function's result depends only on its input arguments, or is affected by outside factors. It is i for “immutable” functions, which always deliver the same result for the same inputs. It is s for “stable” functions, whose results (for fixed inputs) do not change within a scan. It is v for “volatile” functions, whose results might change at any time. (Use v also for functions with side-effects, so that calls to them cannot get optimized away.)
proparallel char
	proparallel tells whether the function can be safely run in parallel mode. It is s for functions which are safe to run in parallel mode without restriction. It is r for functions which can be run in parallel mode, but their execution is restricted to the parallel group leader; parallel worker processes cannot invoke these functions. It is u for functions which are unsafe in parallel mode; the presence of such a function forces a serial execution plan.
pronargs int2
	Number of input arguments
pronargdefaults int2
	Number of arguments that have defaults
prorettype oid (references pg_type.oid)
	Data type of the return value
proargtypes oidvector (references pg_type.oid)
	An array of the data types of the function arguments. This includes only input arguments (including INOUT and VARIADIC arguments), and thus represents the call signature of the function.
proallargtypes oid[] (references pg_type.oid)
	An array of the data types of the function arguments. This includes all arguments (including OUT and INOUT arguments); however, if all the arguments are IN arguments, this field will be null. Note that subscripting is 1-based, whereas for historical reasons proargtypes is subscripted from 0.
proargmodes char[]
	An array of the modes of the function arguments, encoded as i for IN arguments, o for OUT arguments, b for INOUT arguments, v for VARIADIC arguments, t for TABLE arguments. If all the arguments are IN arguments, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes.
proargnames text[]
	An array of the names of the function arguments. Arguments without a name are set to empty strings in the array. If none of the arguments have a name, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes.
proargdefaults pg_node_tree
	Expression trees (in nodeToString() representation) for default values. This is a list with pronargdefaults elements, corresponding to the last N input arguments (i.e., the last N proargtypes positions). If none of the arguments have defaults, this field will be null.
protrftypes oid[] (references pg_type.oid)
	An array of the argument/result data type(s) for which to apply transforms (from the function's TRANSFORM clause). Null if none.
prosrc text
	This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention.
probin text
	Additional information about how to invoke the function. Again, the interpretation is language-specific.
prosqlbody pg_node_tree
	Pre-parsed SQL function body. This is used for SQL-language functions when the body is given in SQL-standard notation rather than as a string literal. It's null in other cases.
proconfig text[]
	Function's local settings for run-time configuration variables
proacl aclitem[]
	Access privileges; see Section Privileges for details

For compiled functions, both built-in and dynamically loaded, prosrc contains the function's C/RUST-language name (link symbol). For SQL-language functions, prosrc contains the function's source text if that is specified as a string literal; but if the function body is specified in SQL-standard style, prosrc is unused (typically it's an empty string) and prosqlbody contains the pre-parsed definition. For all other currently-known language types, prosrc contains the function's source text. probin is null except for dynamically-loaded C/RUST functions, for which it gives the name of the shared library file containing the function.

---

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pg_publication

The catalog pg_publication contains all publications created in the database. For more on publications see Section Publication.

Table 40. pg_publication Columns

Column Type
	Description
oid oid
	Row identifier
pubname name
	Name of the publication
pubname oid (references pg_authid.oid)
	Owner of the publication
puballtables bool
	If true, this publication automatically includes all tables in the database, including any that will be created in the future.
pubinsert bool
	If true, INSERT operations are replicated for tables in the publication.
pubupdate bool
	If true, UPDATE operations are replicated for tables in the publication..
pubdelete bool
	If true, DELETE operations are replicated for tables in the publication.
pubtruncate bool
	If true, TRUNCATE operations are replicated for tables in the publication.
pubviaroot bool
	If true, operations on a leaf partition are replicated using the identity and schema of its topmost partitioned ancestor mentioned in the publication instead of its own.

---

---

pg_publication_namespace

The catalog pg_publication_namespace contains the mapping between schemas and publications in the database. This is a many-to-many mapping.

Table 41.Столбцы pg_publication_namespace Columns

Column Type
	Description
oid oid
	Row identifier
pnpubid oid (references pg_publication.oid)
	Reference to publication
pnnspid oid (references pg_namespace.oid)
	Reference to schema

---

---

pg_publication_rel

The catalog pg_publication_rel contains the mapping between relations and publications in the database. This is a many-to-many mapping. See also pg_publication_tables for a more user-friendly view of this information.

Table 42. pg_publication_rel Columns

Column Type
	Description
oid oid
	Row identifier
prpubid oid (references pg_publication.oid)
	Reference to publication
prrelid oid (references pg_class.oid)
	Reference to relation
prqual pg_node_tree
	Expression tree (in nodeToString() representation) for the relation's publication qualifying condition. Null if there is no publication qualifying condition.
prattrs int2vector (references pg_attribute.attnum)
	This is an array of values that indicates which table columns are part of the publication. For example, a value of 1 3 would mean that the first and the third table columns are published. A null value indicates that all columns are published.

---

---

pg_range

The catalog pg_range stores information about range types. This is in addition to the types' entries in pg_type.

Table 43. pg_range Columns

Column Type
	Description
rngtypid oid (references pg_type.oid)
	OID of the range type
rngsubtype oid (references pg_type.oid)
	OID of the element type (subtype) of this range type
rngmultitypid oid (references pg_type.oid)
	OID of the multirange type for this range type
rngcollation oid (references pg_collation.oid)
	OID of the collation used for range comparisons, or zero if none
rngsubopc oid (references pg_opclass.oid)
	OID of the subtype's operator class used for range comparisons
rngcanonic regproc (references pg_proc.oid)
	OID of the function to convert a range value into canonical form, or zero if none
rngsubdiff regproc (references pg_proc.oid)
	OID of the function to return the difference between two element values as double precision, or zero if none

rngsubopc (plus rngcollation, if the element type is collatable) determines the sort ordering used by the range type. rngcanonical is used when the element type is discrete. rngsubdiff is optional but should be supplied to improve performance of GiST indexes on the range type.

---

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pg_replication_origin

The pg_replication_origin catalog contains all replication origins created. For more on replication origins see Chapter Replication Progress Tracking.

Unlike most system catalogs, pg_replication_origin is shared across all databases of a cluster: there is only one copy of pg_replication_origin per cluster, not one per database.

Table 44. pg_replication_origin Columns

Column Type
	Description
roident oid
	A unique, cluster-wide identifier for the replication origin. Should never leave the system.
roname text
	The external, user defined, name of a replication origin.

---

---

pg_rewrite

The catalog pg_rewrite stores rewrite rules for tables and views.

Table 45. pg_rewrite Columns

Column Type
	Description
oid oid
	Row identifier
rulename name
	Rule name
ev_class oid (references pg_class.oid)
	The table this rule is for
ev_type char
	Event type that the rule is for: 1 = SELECT, 2 = UPDATE, 3 = INSERT, 4 = DELETE
ev_enabled char
	Controls in which session_replication_role modes the rule fires. O = rule fires in “origin” and “local” modes, D = rule is disabled, R = rule fires in “replica” mode, A = rule fires always.
is_instead bool
	True if the rule is an INSTEAD rule
ev_qual pg_node_tree
	Expression tree (in the form of a nodeToString() representation) for the rule's qualifying condition
ev_action pg_node_tree
	Query tree (in the form of a nodeToString() representation) for the rule's action

Note
pg_class.relhasrules must be true if a table has any rules in this catalog.

---

---

pg_seclabel

The catalog pg_seclabel stores security labels on database objects. Security labels can be manipulated with the [SECURITY LABEL] command. For an easier way to view security labels, see pg_seclabels.

See also pg_shseclabel, which performs a similar function for security labels of database objects that are shared across a database cluster.

Table 46. pg_seclabel Columns

Column Type
	Description
objoid oid (references any OID column)
	The OID of the object this security label pertains to
classoid oid (references pg_class.oid)
	The OID of the system catalog this object appears in
objsubid int4
	For a security label on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
provider text
	The label provider associated with this label.
label text
	The security label applied to this object.

---

---

pg_sequence

The catalog pg_sequence contains information about sequences. Some of the information about sequences, such as the name and the schema, is in pg_class.

Table 47. pg_sequence Columns

Column Type
	Description
seqrelid oid (references pg_class.oid)
	The OID of the pg_class entry for this sequence
seqtypid oid (references pg_type.oid)
	Data type of the sequence
seqstart int8
	Start value of the sequence
seqincrement int8
	Increment value of the sequence
seqmax int8
	Maximum value of the sequence
seqmin int8
	Minimum value of the sequence
seqcache int8
	Cache size of the sequence
seqcycle bool
	Whether the sequence cycles

---

---

pg_shdepend

The catalog pg_shdepend records the dependency relationships between database objects and shared objects, such as roles. This information allows QHB to ensure that those objects are unreferenced before attempting to delete them.

See also pg_depend, which performs a similar function for dependencies involving objects within a single database.

Unlike most system catalogs, pg_shdepend is shared across all databases of a cluster: there is only one copy of pg_shdepend per cluster, not one per database.

Table 48. pg_shdepend Columns

Column Type
	Description
dbid oid (references pg_database.oid)
	The OID of the database the dependent object is in, or zero for a shared object
classid oid (references pg_class.oid)
	The OID of the system catalog the dependent object is in
objid oid (references any OID column)
	The OID of the specific dependent object
objsubid int4
	For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero.
refclassid oid (references pg_class.oid)
	The OID of the system catalog the referenced object is in (must be a shared catalog)
refobjid oid (references any OID column)
	The OID of the specific referenced object
deptype char
	A code defining the specific semantics of this dependency relationship; see text

In all cases, a pg_shdepend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype:

SHARED_DEPENDENCY_OWNER (о)
The referenced object (which must be a role) is the owner of the dependent object.

SHARED_DEPENDENCY_ACL (a)
The referenced object (which must be a role) is mentioned in the ACL (access control list, i.e., privileges list) of the dependent object. (A SHARED_DEPENDENCY_ACL entry is not made for the owner of the object, since the owner will have a SHARED_DEPENDENCY_OWNER entry anyway.)

SHARED_DEPENDENCY_POLICY (r)
The referenced object (which must be a role) is mentioned as the target of a dependent policy object.

SHARED_DEPENDENCY_TABLESPACE (t)
The referenced object (which must be a tablespace) is mentioned as the tablespace for a relation that doesn't have storage.

Other dependency flavors might be needed in future. Note in particular that the current definition only supports roles and tablespaces as referenced objects.

As in the pg_depend catalog, most objects created during qhb_bootstrap (or initdb) are considered “pinned”. No entries are made in pg_shdepend that would have a pinned object as either referenced or dependent object.

---

---

pg_shdescription

The catalog pg_shdescription stores optional descriptions (comments) for shared database objects. Descriptions can be manipulated with the [COMMENT] command and viewed with psql's \d commands.

See also pg_description, which performs a similar function for descriptions involving objects within a single database.

Unlike most system catalogs, pg_shdescription is shared across all databases of a cluster: there is only one copy of pg_shdescription per cluster, not one per database.

Table 49. pg_shdescription Columns

Column Type
	Description
objoid oid (references any OID column)
	The OID of the object this description pertains to
classoid oid (references pg_class.oid)
	The OID of the system catalog this object appears in
description text
	Arbitrary text that serves as the description of this object

---

---

pg_shseclabel

The catalog pg_shseclabel stores security labels on shared database objects. Security labels can be manipulated with the [SECURITY LABEL] command. For an easier way to view security labels, see Section pg_seclabels.

See also pg_seclabel, which performs a similar function for security labels involving objects within a single database.

Unlike most system catalogs, pg_shseclabel is shared across all databases of a cluster: there is only one copy of pg_shseclabel per cluster, not one per database.

Table 50. pg_shseclabel Columns

Column Type
	Description
objoid oid (references any OID column)
	The OID of the object this security label pertains to
classoid oid (references pg_class.oid)
	The OID of the system catalog this object appears in
provider text
	The label provider associated with this label.
label text
	The security label applied to this object.

---

---

pg_statistic

The catalog pg_statistic stores statistical data about the contents of the database. Entries are created by [ANALYZE] and subsequently used by the query planner. Note that all the statistical data is inherently approximate, even assuming that it is up-to-date.

Normally there is one entry, with stainherit = false, for each table column that has been analyzed. If the table has inheritance children or partitions, a second entry with stainherit = true is also created. This row represents the column's statistics over the inheritance tree, i.e., statistics for the data you'd see with SELECT column FROM table*, whereas the stainherit = false row represents the results of SELECT column FROM ONLY table.

pg_statistic also stores statistical data about the values of index expressions. These are described as if they were actual data columns; in particular, starelid references the index. No entry is made for an ordinary non-expression index column, however, since it would be redundant with the entry for the underlying table column. Currently, entries for index expressions always have stainherit = false.

Since different kinds of statistics might be appropriate for different kinds of data, pg_statistic is designed not to assume very much about what sort of statistics it stores. Only extremely general statistics (such as nullness) are given dedicated columns in pg_statistic. Everything else is stored in “slots”, which are groups of associated columns whose content is identified by a code number in one of the slot's columns.

pg_statistic should not be readable by the public, since even statistical information about a table's contents might be considered sensitive. (Example: minimum and maximum values of a salary column might be quite interesting.) pg_stats is a publicly readable view on pg_statistic that only exposes information about those tables that are readable by the current user.

Table 51. pg_statistic Columns

Column Type
	Description
starelid oid (references pg_class.oid)
	The table or index that the described column belongs to
staattnum int2 (references pg_attribute.attnum)
	The number of the described column
stainherit bool
	If true, the stats include values from child tables, not just the values in the specified relation
stanullfrac float4
	The fraction of the column's entries that are null
stawidth int4
	The average stored width, in bytes, of nonnull entries
stadistinct float4
	The number of distinct nonnull data values in the column. A value greater than zero is the actual number of distinct values. A value less than zero is the negative of a multiplier for the number of rows in the table; for example, a column in which about 80% of the values are nonnull and each nonnull value appears about twice on average could be represented by stadistinct = -0.4. A zero value means the number of distinct values is unknown.
stakindN int2
	A code number indicating the kind of statistics stored in the Nth “slot” of the pg_statistic row.
staopN oid (references pg_operator.oid)
	An operator used to derive the statistics stored in the Nth “slot”. For example, a histogram slot would show the < operator that defines the sort order of the data. Zero if the statistics kind does not require an operator.
stacollN oid (references pg_collation.oid)
	The collation used to derive the statistics stored in the Nth “slot”. For example, a histogram slot for a collatable column would show the collation that defines the sort order of the data. Zero for noncollatable data.
stanumbersN float4[]
	Numerical statistics of the appropriate kind for the Nth “slot”, or null if the slot kind does not involve numerical values
stavaluesN anyarray
	Column data values of the appropriate kind for the Nth “slot”, or null if the slot kind does not store any data values. Each array's element values are actually of the specific column's data type, or a related type such as an array's element type, so there is no way to define these columns' type more specifically than anyarray.

---

---

pg_statistic_ext

The catalog pg_statistic_ext holds definitions of extended planner statistics. Each row in this catalog corresponds to a statistics object created with [CREATE STATISTICS].

Table 52. pg_statistic_ext Columns

Column Type
	Description
oid oid
	Row identifier
stxrelid oid (references pg_class.oid)
	Table containing the columns described by this object
stxname name
	Name of the statistics object
stxnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this statistics object
stxowner oid (references pg_authid.oid)
	Owner of the statistics object
stxstattarget int4
	stxstattarget controls the level of detail of statistics accumulated for this statistics object by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the maximum of the statistics targets of the referenced columns, if set, or the system default statistics target. Positive values of stxstattarget determine the target number of “most common values” to collect.
stxkeys int2vector (references pg_attribute.attnum)
	An array of attribute numbers, indicating which table columns are covered by this statistics object; for example a value of 1 3 would mean that the first and the third table columns are covered
stxkind char[]
	An array containing codes for the enabled statistics kinds; valid values are: d for n-distinct statistics, f for functional dependency statistics, m for most common values (MCV) list statistics, and e for expression statistics
stxexprs pg_node_tree
	Expression trees (in nodeToString() representation) for statistics object attributes that are not simple column references. This is a list with one element per expression. Null if all statistics object attributes are simple references.

The pg_statistic_ext* entry is filled in completely during [CREATE STATISTICS], but the actual statistical values are not computed then. Subsequent [ANALYZE] commands compute the desired values and populate an entry in the pg_statistic_ext_data catalog.

---

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pg_statistic_ext_data

The catalog pg_statistic_ext_data holds data for extended planner statistics defined in pg_statistic_ext. Each row in this catalog corresponds to a statistics object created with [CREATE STATISTICS].

Normally there is one entry, with stxdinherit = false, for each statistics object that has been analyzed. If the table has inheritance children or partitions, a second entry with stxdinherit = true is also created. This row represents the statistics object over the inheritance tree, i.e., statistics for the data you'd see with SELECT * FROM table*, whereas the stxdinherit = false row represents the results of SELECT * FROM ONLY table.

Like pg_statistic, pg_statistic_ext_data should not be readable by the public, since the contents might be considered sensitive. (Example: most common combinations of values in columns might be quite interesting.) pg_stats_ext is a publicly readable view on pg_statistic_ext_data (after joining with pg_statistic_ext) that only exposes information about those tables and columns that are readable by the current user.

Table 53. pg_statistic_ext_data Columns

Column Type
	Description
stxoid oid (references pg_statistic_ext.oid)
	Extended statistics object containing the definition for this data
stxdinherit bool
	If true, the stats include values from child tables, not just the values in the specified relation
stxdndistinct pg_ndistinct
	N-distinct counts, serialized as pg_ndistinct type
stxddependencies pg_dependencies
	Functional dependency statistics, serialized as pg_dependencies type
stxdmcv pg_mcv_list
	MCV (most-common values) list statistics, serialized as pg_mcv_list type
stxdexpr pg_statistic[]
	Per-expression statistics, serialized as an array of pg_statistic type

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pg_subscription

The catalog pg_subscription contains all existing logical replication subscriptions. For more information about logical replication see Chapter Logical Replication.

Unlike most system catalogs, pg_subscription is shared across all databases of a cluster: there is only one copy of pg_subscription per cluster, not one per database.

Access to the column subconninfo is revoked from normal users, because it could contain plain-text passwords.

Table 54. pg_subscription Columns

Column Type
	Description
oid oid
	Row identifier
subdbid oid (references pg_database.oid)
	OID of the database that the subscription resides in
subskiplsn pg_lsn
	Finish LSN of the transaction whose changes are to be skipped, if a valid LSN; otherwise 0/0.
subname name
	Name of the subscription
subowner oid (references pg_authid.oid)
	Owner of the subscription
subenabled bool
	If true, the subscription is enabled and should be replicating
subbinary bool
	If true, the subscription will request that the publisher send data in binary format
substream bool
	If true, the subscription will allow streaming of in-progress transactions
subtwophasestate char
	State codes for two-phase mode: d = disabled, p = pending enablement, e = enabled
subdisableonerr bool
	If true, the subscription will be disabled if one of its workers detects an error
subconninfo text
	Connection string to the upstream database
subslotname name
	Name of the replication slot in the upstream database (also used for the local replication origin name); null represents NONE.
subsynccommit text
	The synchronous_commit setting for the subscription's workers to use
subpublications text[]
	Array of subscribed publication names. These reference publications defined in the upstream database. For more on publications see Section Publication.

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pg_subscription_rel

The catalog pg_subscription_rel contains the state for each replicated relation in each subscription. This is a many-to-many mapping.

This catalog only contains tables known to the subscription after running either [CREATE SUBSCRIPTION] or [ALTER SUBSCRIPTION ... REFRESH PUBLICATION][ALTER SUBSCRIPTION].

Table 55. pg_subscription_rel Columns

Column Type
	Description
srsubid oid (references pg_subscription.oid)
	Reference to subscription
srrelid oid (references pg_class.oid)
	Reference to relation
srsubstate char
	State code: i = initialize, d = data is being copied, f = finished table copy, s = synchronized, r = ready (normal replication)
srsublsn pg_lsn
	Remote LSN of the state change used for synchronization coordination when in s or r states, otherwise null

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pg_tablespace

The catalog pg_tablespace stores information about the available tablespaces. Tables can be placed in particular tablespaces to aid administration of disk layout.

Unlike most system catalogs, pg_tablespace is shared across all databases of a cluster: there is only one copy of pg_tablespace per cluster, not one per database.

Table 56. pg_tablespace Columns

Column Type
	Description
oid oid
	Row identifier
spcname name
	Tablespace name
spcowner oid (references pg_authid.oid)
	Owner of the tablespace, usually the user who created it
spcacl aclitem[]
	Access privileges; see Section Privileges for details
spcoptions text[]
	Tablespace-level options, as “keyword=value” strings

---

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pg_transform

The catalog pg_transform stores information about transforms, which are a mechanism to adapt data types to procedural languages. See [CREATE TRANSFORM] for more information.

Table 57. pg_transform Columns

Column Type
	Description
oid oid
	Row identifier
trftype oid (references pg_type.oid)
	OID of the data type this transform is for
trflang oid (references pg_language.oid)
	OID of the language this transform is for
trffromsql regproc (references pg_proc.oid)
	The OID of the function to use when converting the data type for input to the procedural language (e.g., function parameters). Zero is stored if the default behavior should be used.
trftosql regproc (references pg_proc.oid)
	The OID of the function to use when converting output from the procedural language (e.g., return values) to the data type. Zero is stored if the default behavior should be used.

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pg_trigger

The catalog pg_trigger stores triggers on tables and views. See [CREATE TRIGGER] for more information.

Table 58. pg_trigger Columns

Column Type
	Description
oid oid
	Row identifier
tgrelid oid (references pg_class.oid)
	The table this trigger is on
tgparentid oid (references pg_trigger.oid)
	Parent trigger that this trigger is cloned from (this happens when partitions are created or attached to a partitioned table); zero if not a clone
tgname name
	Trigger name (must be unique among triggers of same table)
tgfoid oid (references pg_proc.oid)
	The function to be called
tgtype int2
	Bit mask identifying trigger firing conditions
tgenabled char
	Controls in which session_replication_role modes the trigger fires. O = trigger fires in “origin” and “local” modes, D = trigger is disabled, R = trigger fires in “replica” mode, A = trigger fires always.
tgisinternal bool
	True if trigger is internally generated (usually, to enforce the constraint identified by tgconstraint)
tgconstrrelid oid (references pg_class.oid)
	The table referenced by a referential integrity constraint (zero if trigger is not for a referential integrity constraint)
tgconstrindid oid (references pg_class.oid)
	The index supporting a unique, primary key, referential integrity, or exclusion constraint (zero if trigger is not for one of these types of constraint)
tgconstraint oid (references pg_constraint.oid)
	The pg_constraint entry associated with the trigger (zero if trigger is not for a constraint)
tgdeferrable bool
	True if constraint trigger is deferrable
tginitdeferred bool
	True if constraint trigger is initially deferred
tgnargs int2
	Number of argument strings passed to trigger function
tgattr int2vector (references pg_attribute.attnum)
	Column numbers, if trigger is column-specific; otherwise an empty array
tgargs bytea
	Argument strings to pass to trigger, each NULL-terminated
tgqual pg_node_tree
	Expression tree (in nodeToString() representation) for the trigger's WHEN condition, or null if none
tgoldtable name
	Имя предложения REFERENCING для OLD TABLE или NULL, если такового нет
tgnewtable name
	Имя предложения REFERENCING для NEW TABLE или NULL, если такового нет

В настоящее время триггеры, специфичные для столбцов, поддерживаются только для событий UPDATE, поэтому поле tgattr актуально только для этого типа событий. Поле tgtype может также содержать биты для других типов событий, но считается, что они распространяются только на таблицы, независимо от значения поля tgattr.

Примечание
Когда поле tgconstraint имеет отличное от нуля значение, поля tgconstrrelid, tgconstrindid, tgdeferrable и tginitdeferred в основном дублируют ссылочную запись в каталоге pg_constraint. Тем не менее неоткладываемый триггер может быть связан с откладываемым ограничением: ограничения внешнего ключа могут иметь как откладываемые, так и неоткладываемые триггеры.

Примечание
pg_class.relhastriggers must be true if a relation has any triggers in this catalog.

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pg_ts_config

The pg_ts_config catalog contains entries representing text search configurations. A configuration specifies a particular text search parser and a list of dictionaries to use for each of the parser's output token types. The parser is shown in the pg_ts_config entry, but the token-to-dictionary mapping is defined by subsidiary entries in pg_ts_config_map.

QHB's text search features are described at length in Chapter Full Text Search.

Table 59. pg_ts_config Columns

Column Type
	Description
oid oid
	Row identifier
cfgname name
	Text search configuration name
cfgnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this configuration
cfgowner oid (references pg_authid.oid)
	Owner of the configuration
cfgparser oid (references pg_ts_parser.oid)
	The OID of the text search parser for this configuration

---

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pg_ts_config_map

The pg_ts_config_map catalog contains entries showing which text search dictionaries should be consulted, and in what order, for each output token type of each text search configuration's parser.

QHB's text search features are described at length in Chapter Full Text Search.

Table 60. pg_ts_config_map Columns

Column Type
	Description
mapcfg oid (references pg_ts_config.oid)
	The OID of the pg_ts_config entry owning this map entry
maptokentype int4
	A token type emitted by the configuration's parser
mapseqno int4
	Order in which to consult this entry (lower mapseqnos first)
mapdict oid (references pg_ts_dict.oid)
	The OID of the text search dictionary to consult

---

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pg_ts_dict

The pg_ts_dict catalog contains entries defining text search dictionaries. A dictionary depends on a text search template, which specifies all the implementation functions needed; the dictionary itself provides values for the user-settable parameters supported by the template. This division of labor allows dictionaries to be created by unprivileged users. The parameters are specified by a text string dictinitoption, whose format and meaning vary depending on the template.

QHB's text search features are described at length in Chapter Full Text Search.

Table 61. pg_ts_dict Columns

Column Type
	Description
oid oid
	Row identifier
dictname name
	Text search dictionary name
dictnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this dictionary
dictowner oid (references pg_authid.oid)
	Owner of the dictionary
dicttemplate oid (references pg_ts_template.oid)
	The OID of the text search template for this dictionary
dictinitoption text
	Initialization option string for the template

---

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pg_ts_parser

The pg_ts_parser catalog contains entries defining text search parsers. A parser is responsible for splitting input text into lexemes and assigning a token type to each lexeme. Since a parser must be implemented by C/RUST-language- level functions, creation of new parsers is restricted to database superusers.

QHB's text search features are described at length in Chapter Full Text Search.

Table 62. pg_ts_parser Columns

Column Type
	Description
oid oid
	Row identifier
prsname name
	Text search parser name
prsnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this parser
prsstart regproc (references pg_proc.oid)
	OID of the parser's startup function
prstoken regproc (references pg_proc.oid)
	OID of the parser's next-token function
prsend regproc (references pg_proc.oid)
	OID of the parser's shutdown function
prsheadline regproc (references pg_proc.oid)
	OID of the parser's headline function (zero if none)
prslextype regproc (references pg_proc.oid)
	OID of the parser's lextype function

---

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pg_ts_template

The pg_ts_template catalog contains entries defining text search templates. A template is the implementation skeleton for a class of text search dictionaries. Since a template must be implemented by C/RUST-language-level functions, creation of new templates is restricted to database superusers.

QHB's text search features are described at length in Chapter Full Text Search.

Table 63. pg_ts_template Columns

Column Type
	Description
oid oid
	Row identifier
tmplname name
	Text search template name
tmplnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this template
tmplinit regproc (references pg_proc.oid)
	OID of the template's initialization function (zero if none)
tmpllexize regproc (references pg_proc.oid)
	OID of the template's lexize function

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pg_type

The catalog pg_type stores information about data types. Base types and enum types (scalar types) are created with [CREATE TYPE], and domains with [CREATE DOMAIN]. A composite type is automatically created for each table in the database, to represent the row structure of the table. It is also possible to create composite types with CREATE TYPE AS.

Table 64. pg_type Columns

Column Type
	Description
oid oid
	Row identifier
typname name
	Data type name
typnamespace oid (references pg_namespace.oid)
	The OID of the namespace that contains this type
typowner oid (references pg_authid.oid)
	Owner of the type
typlen int2
	For a fixed-size type, typlen is the number of bytes in the internal representation of the type. But for a variable-length type, typlen is negative. -1 indicates a “varlena” type (one that has a length word), -2 indicates a null-terminated C/RUST string.
typbyval bool
	typbyval determines whether internal routines pass a value of this type by value or by reference. typbyval had better be false if typlen is not 1, 2, or 4 (or 8 on machines where Datum is 8 bytes). Variable-length types are always passed by reference. Note that typbyval can be false even if the length would allow pass-by-value.
typtype char
	typtype is b for a base type, c for a composite type (e.g., a table's row type), d for a domain, e for an enum type, p for a pseudo-type, r for a range type, or m for a multirange type. See also typrelid and typbasetype.
typcategory char
	typcategory is an arbitrary classification of data types that is used by the parser to determine which implicit casts should be “preferred”. See Table 65.
typispreferred bool
	True if the type is a preferred cast target within its typcategory
typisdefined bool
	True if the type is defined, false if this is a placeholder entry for a not-yet-defined type. When typisdefined is false, nothing except the type name, namespace, and OID can be relied on.
typdelim char
	Character that separates two values of this type when parsing array input. Note that the delimiter is associated with the array element data type, not the array data type.
typrelid oid (references pg_class.oid)
	If this is a composite type (see typtype), then this column points to the pg_class entry that defines the corresponding table. (For a free-standing composite type, the pg_class entry doesn't really represent a table, but it is needed anyway for the type's pg_attribute entries to link to.) Zero for non-composite types.
typsubscript regproc (references pg_proc.oid)
	Subscripting handler function's OID, or zero if this type doesn't support subscripting. Types that are “true” array types have typsubscript = array_subscript_handler, but other types may have other handler functions to implement specialized subscripting behavior.
typelem oid (references pg_type.oid)
	If typelem is not zero then it identifies another row in pg_type, defining the type yielded by subscripting. This should be zero if typsubscript is zero. However, it can be zero when typsubscript isn't zero, if the handler doesn't need typelem to determine the subscripting result type. Note that a typelem dependency is considered to imply physical containment of the element type in this type; so DDL changes on the element type might be restricted by the presence of this type.
typarray oid (references pg_type.oid)
	If typarray is not zero then it identifies another row in pg_type, which is the “true” array type having this type as element
typinput regproc (references pg_proc.oid)
	Input conversion function (text format)
typoutput regproc (references pg_proc.oid)
	Output conversion function (text format)
typreceive regproc (references pg_proc.oid)
	Input conversion function (binary format), or zero if none
typsend regproc (references pg_proc.oid)
	Output conversion function (binary format), or zero if none
typmodin regproc (references pg_proc.oid)
	Type modifier input function, or zero if type does not support modifiers
typmodout regproc (references pg_proc.oid)
	Type modifier output function, or zero to use the standard format
typanalyze regproc (references pg_proc.oid)
	Custom ANALYZE function, or zero to use the standard function
typalign char
	typalign is the alignment required when storing a value of this type. It applies to storage on disk as well as most representations of the value inside QHB. When multiple values are stored consecutively, such as in the representation of a complete row on disk, padding is inserted before a datum of this type so that it begins on the specified boundary. The alignment reference is the beginning of the first datum in the sequence. Possible values are: c = char alignment, i.e., no alignment needed. s = short alignment (2 bytes on most machines). i = int alignment (4 bytes on most machines). d = double alignment (8 bytes on many machines, but by no means all).
typstorage char
	typstorage tells for varlena types (those with typlen = -1) if the type is prepared for toasting and what the default strategy for attributes of this type should be. Possible values are: p (plain): Values must always be stored plain (non-varlena types always use this value). e (external): Values can be stored in a secondary “TOAST” relation (if relation has one, see pg_class.reltoastrelid). m (main): Values can be compressed and stored inline. x (extended): Values can be compressed and/or moved to a secondary relation. x is the usual choice for toast-able types. Note that m values can also be moved out to secondary storage, but only as a last resort (e and x values are moved first).
typnotnull bool
	typnotnull represents a not-null constraint on a type. Used for domains only.
typbasetype oid (references pg_type.oid)
	If this is a domain (see typtype), then typbasetype identifies the type that this one is based on. Zero if this type is not a domain.
typtypmod int4
	Domains use typtypmod to record the typmod to be applied to their base type (-1 if base type does not use a typmod). -1 if this type is not a domain.
typndims int4
	typndims is the number of array dimensions for a domain over an array (that is, typbasetype is an array type). Zero for types other than domains over array types.
typcollation oid (references pg_collation.oid)
	typcollation specifies the collation of the type. If the type does not support collations, this will be zero. A base type that supports collations will have a nonzero value here, typically DEFAULT_COLLATION_OID. A domain over a collatable type can have a collation OID different from its base type's, if one was specified for the domain.
typdefaultbin pg_node_tree
	If typdefaultbin is not null, it is the nodeToString() representation of a default expression for the type. This is only used for domains.
typdefault text
	typdefault is null if the type has no associated default value. If typdefaultbin is not null, typdefault must contain a human-readable version of the default expression represented by typdefaultbin. If typdefaultbin is null and typdefault is not, then typdefault is the external representation of the type's default value, which can be fed to the type's input converter to produce a constant.
typacl aclitem[]
	Access privileges; see Section Privileges for details

Note
For fixed-width types used in system tables, it is critical that the size and alignment defined in pg_type agree with the way that the compiler will lay out the column in a structure representing a table row.

Table 65 lists the system-defined values of typcategory. Any future additions to this list will also be upper-case ASCII letters. All other ASCII characters are reserved for user-defined categories.

Table 65. typcategory Codes

Code	Category
A	Array types
B	Boolean types
C	Composite types
D	Date/time types
E	Enum types
G	Geometric types
I	Network address types
N	Numeric types
P	Pseudo-types
R	Range types
S	String types
T	Timespan types
U	User-defined types
V	Bit-string types
X	unknown type
Z	Internal-use types

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pg_user_mapping

The catalog pg_user_mapping stores the mappings from local user to remote. Access to this catalog is restricted from normal users, use the view pg_user_mappings instead.

Table 66. pg_user_mapping Columns

Column Type
	Description
oid oid
	Row identifier
umuser oid (references pg_authid.oid)
	OID of the local role being mapped, or zero if the user mapping is public
umserver oid (references pg_foreign_server.oid)
	The OID of the foreign server that contains this mapping
umoptions text[]
	User mapping specific options, as “keyword=value” strings