System Information Functions and Operators
The functions described in this section are used to obtain various information about a QHB installation.
Session Information Functions
This section shows several functions that extract session and system information.
In addition to the functions listed in this section, there are a number of functions related to the statistics system that also provide system information. See Section Statistics Functions for more information.
current_catalog or current_database
current_catalog → name
current_database () → name
Returns the name of the current database. (Databases are called “catalogs” in the SQL standard, so current_catalog is the standard's spelling.)
current_query
current_query () → text
Returns the text of the currently executing query, as submitted by the client (which might contain more than one statement).
current_role
current_role → name
This is equivalent to current_user.
current_schema
current_schema → name
current_schema () → name
Returns the name of the schema that is first in the search path (or a null value if the search path is empty). This is the schema that will be used for any tables or other named objects that are created without specifying a target schema.
current_schemas
current_schemas ( include_implicit boolean ) → name[]
Returns an array of the names of all schemas presently in the effective search path, in their priority order. (Items in the current search_path setting that do not correspond to existing, searchable schemas are omitted.) If the Boolean argument is true, then implicitly-searched system schemas such as pg_catalog are included in the result.
current_user
current_user → name
Returns the user name of the current execution context.
inet_client_addr
inet_client_addr () → inet
Returns the IP address of the current client, or NULL if the current connection is via a Unix-domain socket.
inet_client_port
inet_client_port () → integer
Returns the IP port number of the current client, or NULL if the current connection is via a Unix-domain socket.
inet_server_addr
inet_server_addr () → inet
Returns the IP address on which the server accepted the current connection, or NULL if the current connection is via a Unix-domain socket.
inet_server_port
inet_server_port () → integer
Returns the IP port number on which the server accepted the current connection, or NULL if the current connection is via a Unix-domain socket.
pg_backend_pid
pg_backend_pid () → integer
Returns the process ID of the server process attached to the current session.
pg_blocking_pids
pg_blocking_pids ( integer ) → integer[]
Returns an array of the process ID(s) of the sessions that are blocking the server process with the specified process ID from acquiring a lock, or an empty array if there is no such server process or it is not blocked.
One server process blocks another if it either holds a lock that conflicts with the blocked process's lock request (hard block), or is waiting for a lock that would conflict with the blocked process's lock request and is ahead of it in the wait queue (soft block). When using parallel queries the result always lists client-visible process IDs (that is, pg_backend_pid results) even if the actual lock is held or awaited by a child worker process. As a result of that, there may be duplicated PIDs in the result. Also note that when a prepared transaction holds a conflicting lock, it will be represented by a zero process ID.
Frequent calls to this function could have some impact on database performance, because it needs exclusive access to the lock manager's shared state for a short time.
pg_conf_load_time
pg_conf_load_time () → timestamp with time zone
Returns the time when the server configuration files were last loaded. If the current session was alive at the time, this will be the time when the session itself re-read the configuration files (so the reading will vary a little in different sessions). Otherwise it is the time when the qhbmaster process re-read the configuration files.
pg_current_logfile
pg_current_logfile ( [ text ] ) → text
Returns the path name of the log file currently in use by the logging collector. The path includes the log_directory directory and the individual log file name. The result is NULL if the logging collector is disabled. When multiple log files exist, each in a different format, pg_current_logfile without an argument returns the path of the file having the first format found in the ordered list: stderr, csvlog, jsonlog. NULL is returned if no log file has any of these formats. To request information about a specific log file format, supply either csvlog, jsonlog or stderr as the value of the optional parameter. The result is NULL if the log format requested is not configured in log_destination. The result reflects the contents of the current_logfiles file.
pg_my_temp_schema
pg_my_temp_schema () → oid
Returns the OID of the current session's temporary schema, or zero if it has none (because it has not created any temporary tables).
pg_is_other_temp_schema
pg_is_other_temp_schema ( oid ) → boolean
Returns true if the given OID is the OID of another session's temporary schema. (This can be useful, for example, to exclude other sessions' temporary tables from a catalog display.)
pg_jit_available
pg_jit_available () → boolean
Returns true if a JIT compiler extension is available (see Chapter Just-in-Time Compilation (JIT)) and the jit configuration parameter is set to on.
pg_listening_channels
pg_listening_channels () → setof text
Returns the set of names of asynchronous notification channels that the current session is listening to.
pg_notification_queue_usage
pg_notification_queue_usage () → double precision
Returns the fraction (0–1) of the asynchronous notification queue's maximum size that is currently occupied by notifications that are waiting to be processed. See LISTEN and NOTIFY for more information.
pg_qhbmaster_start_time
pg_qhbmaster_start_time () → timestamp with time zone
Returns the time when the server started.
pg_safe_snapshot_blocking_pids
pg_safe_snapshot_blocking_pids ( integer ) → integer[]
Returns an array of the process ID(s) of the sessions that are blocking the server process with the specified process ID from acquiring a safe snapshot, or an empty array if there is no such server process or it is not blocked.
A session running a SERIALIZABLE transaction blocks a SERIALIZABLE READ ONLY DEFERRABLE transaction from acquiring a snapshot until the latter determines that it is safe to avoid taking any predicate locks. See Section Serializable Isolation Level for more information about serializable and deferrable transactions.
Frequent calls to this function could have some impact on database performance, because it needs access to the predicate lock manager's shared state for a short time.
pg_trigger_depth
pg_trigger_depth () → integer
Returns the current nesting level of QHB triggers (0 if not called, directly or indirectly, from inside a trigger).
session_user
session_user → name
Returns the session user's name.
system_user
system_user → text
Returns the authentication method and the identity (if any) that the user presented during the authentication cycle before they were assigned a database role. It is represented as auth_method:identity or NULL if the user has not been authenticated (for example if Trust authentication has been used).
user
user → name
This is equivalent to current_user.
version
version () → text
Returns a string describing the QHB server's version. You can also get this information from server_version, or for a machine-readable version use server_version_num. Software developers should use server_version_num or PQserverVersion instead of parsing the text version.
Notes
current_catalog, current_role, current_schema, current_user, session_user, and user have special syntactic status in SQL: they must be called without trailing parentheses. In QHB, parentheses can optionally be used with current_schema, but not with the others.
The session_user is normally the user who initiated the current database connection; but superusers can change this setting with SET SESSION AUTHORIZATION. The current_user is the user identifier that is applicable for permission checking. Normally it is equal to the session user, but it can be changed with SET ROLE. It also changes during the execution of functions with the attribute SECURITY DEFINER. In Unix parlance, the session user is the “real user” and the current user is the “effective user”. current_role and user are synonyms for current_user. (The SQL standard draws a distinction between current_role and current_user, but QHB does not, since it unifies users and roles into a single kind of entity.)
Access Privilege Inquiry Functions
This section lists functions that allow querying object access privileges programmatically. (See Section Privileges for more information about privileges.) In these functions, the user whose privileges are being inquired about can be specified by name or by OID (pg_authid.oid), or if the name is given as public then the privileges of the PUBLIC pseudo-role are checked. Also, the user argument can be omitted entirely, in which case the current_user is assumed. The object that is being inquired about can be specified either by name or by OID, too. When specifying by name, a schema name can be included if relevant. The access privilege of interest is specified by a text string, which must evaluate to one of the appropriate privilege keywords for the object's type (e.g., SELECT). Optionally, WITH GRANT OPTION can be added to a privilege type to test whether the privilege is held with grant option. Also, multiple privilege types can be listed separated by commas, in which case the result will be true if any of the listed privileges is held. (Case of the privilege string is not significant, and extra whitespace is allowed between but not within privilege names.) Some examples:
SELECT has_table_privilege('myschema.mytable', 'select');
SELECT has_table_privilege('joe', 'mytable', 'INSERT, SELECT WITH GRANT OPTION');
has_any_column_privilege
has_any_column_privilege ( [ username или oid, ]tabletext или oid,privilege text ) → boolean
Does user have privilege for any column of table? This succeeds either if the privilege is held for the whole table, or if there is a column-level grant of the privilege for at least one column. Allowable privilege types are SELECT, INSERT, UPDATE, and REFERENCES.
has_column_privilege
has_column_privilege ( [ username или oid, ]tabletext или oid,columntext или smallint,privilege text ) → boolean
Does user have privilege for the specified table column? This succeeds either if the privilege is held for the whole table, or if there is a column-level grant of the privilege for the column. The column can be specified by name or by attribute number (pg_attribute.attnum). Allowable privilege types are SELECT, INSERT, UPDATE, and REFERENCES.
has_database_privilege
has_database_privilege ( [ username или oid, ]databasetext или oid,privilege text ) → boolean
Does user have privilege for database? Allowable privilege types are CREATE, CONNECT, TEMPORARY, and TEMP (which is equivalent to TEMPORARY).
has_foreign_data_wrapper_privilege
has_foreign_data_wrapper_privilege ( [ username или oid, ]fdwtext или oid,privilege text ) → boolean
Does user have privilege for foreign-data wrapper? The only allowable privilege type is USAGE.
has_function_privilege
has_function_privilege ( [ username или oid, ]functiontext или oid,privilege text ) → boolean
Does user have privilege for function? The only allowable privilege type is EXECUTE.
When specifying a function by name rather than by OID, the allowed input is the same as for the regprocedure data type (see Section Object Identifier Types). An example is:
SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute');
has_language_privilege
has_language_privilege ( [ username или oid, ]languagetext или oid,privilege text ) → boolean
Does user have privilege for language? The only allowable privilege type is USAGE.
has_parameter_privilege
has_parameter_privilege ( [ username или oid, ]parametertext,privilege text ) → boolean
Does user have privilege for configuration parameter? The parameter name is case-insensitive. Allowable privilege types are SET and ALTER SYSTEM.
has_schema_privilege
has_schema_privilege ( [ username или oid, ]schematext или oid,privilege text ) → boolean
Does user have privilege for schema? Allowable privilege types are CREATE and USAGE.
has_sequence_privilege
has_sequence_privilege ( [ username или oid, ]sequencetext или oid,privilege text ) → boolean
Does user have privilege for sequence? Allowable privilege types are USAGE, SELECT, and UPDATE.
has_server_privilege
has_server_privilege ( [ username или oid, ]servertext или oid,privilege text ) → boolean
Does user have privilege for foreign server? The only allowable privilege type is USAGE.
has_table_privilege
has_table_privilege ( [ username или oid, ]tabletext или oid,privilege text ) → boolean
Does user have privilege for table? Allowable privilege types are SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, and TRIGGER.
has_tablespace_privilege
has_tablespace_privilege ( [ username или oid, ]tablespacetext или oid,privilege text ) → boolean
Does user have privilege for tablespace? The only allowable privilege type is CREATE.
has_type_privilege
has_type_privilege ( [ username или oid, ]typetext или oid,privilege text ) → boolean
Does user have privilege for data type? The only allowable privilege type is USAGE. When specifying a type by name rather than by OID, the allowed input is the same as for the regtype data type (see Section Object Identifier Types).
pg_has_role
pg_has_role ( [ username или oid, ]roletext или oid,privilege text ) → boolean
Does user have privilege for role? Allowable privilege types are MEMBER, USAGE,
and SET. MEMBER denotes direct or indirect membership in the role without
regard to what specific privileges may be conferred. USAGE denotes whether the
privileges of the role are immediately available without doing SET ROLE, while
SET denotes whether it is possible to change to the role using the SET ROLE
command. WITH ADMIN OPTION or WITH GRANT OPTION can be added to any of
these privilege types to test whether the ADMIN privilege is held (all six
spellings test the same thing). This function does not allow the special case of
setting user to public, because the PUBLIC pseudo-role can never be a
member of real roles.
row_security_active
row_security_active ( table text или oid ) → boolean
Is row-level security active for the specified table in the context of the current user and current environment?
aclitem Operators
This section shows the operators available for the aclitem type, which is the catalog representation of access privileges. See Section Privileges for information about how to read access privilege values.
aclitem = aclitem → boolean
Are aclitems equal? (Notice that type aclitem lacks the usual set of comparison operators; it has only equality. In turn, aclitem arrays can only be compared for equality.)
'calvin=r*w/hobbes'::aclitem = 'calvin=r*w*/hobbes'::aclitem → f
aclitem[] @> aclitem → boolean
Does array contain the specified privileges? (This is true if there is an array entry that matches the aclitem's grantee and grantor, and has at least the specified set of privileges.)
'{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] @> 'calvin=r*/hobbes'::aclitem → t
aclitem[] ~ aclitem → boolean
This is a deprecated alias for @>.
'{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] ~ 'calvin=r*/hobbes'::aclitem → t
aclitem Functions
This section shows some additional functions to manage the aclitem type.
acldefault
acldefault ( type"char",ownerId oid ) → aclitem[]
Constructs an aclitem array holding the default access privileges for an object of type type belonging to the role with OID ownerId. This represents the access privileges that will be assumed when an object's ACL entry is null. (The default access privileges are described in Section Privileges.) The type parameter must be one of 'c' for COLUMN, 'r' for TABLE and table-like objects, 's' for SEQUENCE, 'd' for DATABASE, 'f' for FUNCTION or PROCEDURE, 'l' for LANGUAGE, 'L' for LARGE OBJECT, 'n' for SCHEMA, 'p' for PARAMETER, 't' for TABLESPACE, 'F' for FOREIGN DATA WRAPPER, 'S' for FOREIGN SERVER, or 'T' for TYPE or DOMAIN.
aclexplode
aclexplode ( aclitem[] ) → setof record ( grantoroid,granteeoid,privilege_typetext,is_grantable boolean )
Returns an aclitem array as a set of rows. If the grantee is the pseudo-role PUBLIC, it is represented by zero in the grantee column. Each granted privilege is represented as SELECT, INSERT, etc (see Table ACL Privilege Abbreviations for a full list). Note that each privilege is broken out as a separate row, so only one keyword appears in the privilege_type column.
makeaclitem
makeaclitem ( granteeoid,grantoroid,privilegestext,is_grantable boolean ) → aclitem
Constructs an aclitem with the given properties. privileges is a comma- separated list of privilege names such as SELECT, INSERT, etc, all of which are set in the result. (Case of the privilege string is not significant, and extra whitespace is allowed between but not within privilege names.)
Schema Visibility Inquiry Functions
This section shows functions that determine whether a certain object is visible in the current schema search path. For example, a table is said to be visible if its containing schema is in the search path and no table of the same name appears earlier in the search path. This is equivalent to the statement that the table can be referenced by name without explicit schema qualification. Thus, to list the names of all visible tables:
SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
For functions and operators, an object in the search path is said to be visible if there is no object of the same name and argument data type(s) earlier in the path. For operator classes and families, both the name and the associated index access method are considered.
pg_collation_is_visible
pg_collation_is_visible ( collation oid ) → boolean
Is collation visible in search path?
pg_conversion_is_visible
pg_conversion_is_visible ( conversion oid ) → boolean
Is conversion visible in search path?
pg_function_is_visible
pg_function_is_visible ( function oid ) → boolean
Is function visible in search path? (This also works for procedures and aggregates.)
pg_opclass_is_visible
pg_opclass_is_visible ( opclass oid ) → boolean
Is operator class visible in search path?
pg_operator_is_visible
pg_operator_is_visible ( operator oid ) → boolean
Is operator visible in search path?
pg_opfamily_is_visible
pg_opfamily_is_visible ( opfamily oid ) → boolean
Is operator family visible in search path?
pg_statistics_obj_is_visible
pg_statistics_obj_is_visible ( stat oid ) → boolean
Is statistics object visible in search path?
pg_table_is_visible
pg_table_is_visible ( table oid ) → boolean
Is table visible in search path? (This works for all types of relations, including views, materialized views, indexes, sequences and foreign tables.)
pg_ts_config_is_visible
pg_ts_config_is_visible ( config oid ) → boolean
Is text search configuration visible in search path?
pg_ts_dict_is_visible
pg_ts_dict_is_visible ( dict oid ) → boolean
Is text search dictionary visible in search path?
pg_ts_parser_is_visible
pg_ts_parser_is_visible ( parser oid ) → boolean
Is text search parser visible in search path?
pg_ts_template_is_visible
pg_ts_template_is_visible ( template oid ) → boolean
Is text search template visible in search path?
pg_type_is_visible
pg_type_is_visible ( type oid ) → boolean
Is type (or domain) visible in search path?
Note
All these functions require object OIDs to identify the object to be checked. If you want to test an object by name, it is convenient to use the OID alias types (regclass, regtype, regprocedure, regoperator, regconfig, or regdictionary), for example:
SELECT pg_type_is_visible('myschema.widget'::regtype);
Note that it would not make much sense to test a non-schema-qualified type name in this way — if the name can be recognized at all, it must be visible.
System Catalog Information Functions
This section lists functions that extract information from the system catalogs.
format_type
format_type ( typeoid,typemod integer ) → text
Returns the SQL name for a data type that is identified by its type OID and possibly a type modifier. Pass NULL for the type modifier if no specific modifier is known.
pg_char_to_encoding
pg_char_to_encoding ( encoding name ) → integer
Converts the supplied encoding name into an integer representing the internal identifier used in some system catalog tables. Returns -1 if an unknown encoding name is provided.
pg_encoding_to_char
pg_encoding_to_char ( encoding integer ) → name
Converts the integer used as the internal identifier of an encoding in some system catalog tables into a human-readable string. Returns an empty string if an invalid encoding number is provided.
pg_get_catalog_foreign_keys
pg_get_catalog_foreign_keys () → setof record ( fktableregclass,fkcolstext[],pktableregclass,pkcolstext[],is_arrayboolean,is_opt boolean )
Returns a set of records describing the foreign key relationships that exist within the QHB system catalogs. The fktable column contains the name of the referencing catalog, and the fkcols column contains the name(s) of the referencing column(s). Similarly, the pktable column contains the name of the referenced catalog, and the pkcols column contains the name(s) of the referenced column(s). If is_array is true, the last referencing column is an array, each of whose elements should match some entry in the referenced catalog. If is_opt is true, the referencing column(s) are allowed to contain zeroes instead of a valid reference.
pg_get_constraintdef
pg_get_constraintdef ( constraintoid [,pretty boolean ] ) → text
Reconstructs the creating command for a constraint. (This is a decompiled reconstruction, not the original text of the command.)
pg_get_expr
pg_get_expr ( exprpg_node_tree,relationoid [,pretty boolean ] ) → text
Decompiles the internal form of an expression stored in the system catalogs, such as the default value for a column. If the expression might contain Vars, specify the OID of the relation they refer to as the second parameter; if no Vars are expected, passing zero is sufficient.
pg_get_functiondef
pg_get_functiondef ( func oid ) → text
Reconstructs the creating command for a function or procedure. (This is a
decompiled reconstruction, not the original text of the command.) The result is
a complete CREATE OR REPLACE FUNCTION or CREATE OR REPLACE PROCEDURE statement.
pg_get_function_arguments
pg_get_function_arguments ( func oid ) → text
Reconstructs the argument list of a function or procedure, in the form it would
need to appear in within CREATE FUNCTION (including default values).
pg_get_function_identity_arguments
pg_get_function_identity_arguments ( func oid ) → text
Reconstructs the argument list necessary to identify a function or procedure, in
the form it would need to appear in within commands such as ALTER FUNCTION.
This form omits default values.
pg_get_function_result
pg_get_function_result ( func oid ) → text
Reconstructs the RETURNS clause of a function, in the form it would need to
appear in within CREATE FUNCTION. Returns NULL for a procedure.
pg_get_indexdef
pg_get_indexdef ( indexoid [,columninteger,pretty boolean ] ) → text
Reconstructs the creating command for an index. (This is a decompiled reconstruction, not the original text of the command.) If column is supplied and is not zero, only the definition of that column is reconstructed.
pg_get_keywords
pg_get_keywords () → setof record ( wordtext,catcode"char",barelabelboolean,catdesctext,baredesc text )
Returns a set of records describing the SQL keywords recognized by the server.
The word column contains the keyword. The catcode column contains a
category code: U for an unreserved keyword, C for a keyword that can be
a column name, T for a keyword that can be a type or function name, or R
for a fully reserved keyword. The barelabel column contains true if the
keyword can be used as a “bare” column label in SELECT lists, or false if it
can only be used after AS. The catdesc column contains a possibly-
localized string describing the keyword's category. The baredesc column
contains a possibly-localized string describing the keyword's column label status.
pg_get_partkeydef
pg_get_partkeydef ( table oid ) → text
Reconstructs the definition of a partitioned table's partition key, in the form
it would have in the PARTITION BY clause of CREATE TABLE. (This is a
decompiled reconstruction, not the original text of the command.)
pg_get_ruledef
pg_get_ruledef ( ruleoid [,pretty boolean ] ) → text
Reconstructs the creating command for a rule. (This is a decompiled reconstruction, not the original text of the command.)
pg_get_serial_sequence
pg_get_serial_sequence ( tabletext,column text ) → text
Returns the name of the sequence associated with a column, or NULL if no
sequence is associated with the column. If the column is an identity column, the
associated sequence is the sequence internally created for that column. For
columns created using one of the serial types (serial, smallserial, bigserial),
it is the sequence created for that serial column definition. In the latter case,
the association can be modified or removed with ALTER SEQUENCE OWNED BY. (This
function probably should have been called pg_get_owned_sequence; its current
name reflects the fact that it has historically been used with serial-type
columns.) The first parameter is a table name with optional schema, and the second
parameter is a column name. Because the first parameter potentially contains both
schema and table names, it is parsed per usual SQL rules, meaning it is lower-cased
by default. The second parameter, being just a column name, is treated literally
and so has its case preserved. The result is suitably formatted for passing to
the sequence functions (see Section Sequence Manipulation Functions).
A typical use is in reading the current value of the sequence for an identity or serial column, for example:
SELECT currval(pg_get_serial_sequence('sometable', 'id'));
pg_get_statisticsobjdef
pg_get_statisticsobjdef ( statobj oid ) → text
Reconstructs the creating command for an extended statistics object. (This is a decompiled reconstruction, not the original text of the command.)
pg_get_triggerdef
pg_get_triggerdef ( triggeroid [,pretty boolean ] ) → text
Reconstructs the creating command for a trigger. (This is a decompiled reconstruction, not the original text of the command.)
pg_get_userbyid
pg_get_userbyid ( role oid ) → name
Returns a role's name given its OID.
pg_get_viewdef
pg_get_viewdef ( viewoid [,pretty boolean ] ) → text
Reconstructs the underlying SELECT command for a view or materialized view.
(This is a decompiled reconstruction, not the original text of the command.)
pg_get_viewdef ( viewoid,wrap_column integer ) → text
Reconstructs the underlying SELECT command for a view or materialized view.
(This is a decompiled reconstruction, not the original text of the command.) In
this form of the function, pretty-printing is always enabled, and long lines are
wrapped to try to keep them shorter than the specified number of columns.
pg_get_viewdef ( viewtext [,pretty boolean ] ) → text
Reconstructs the underlying SELECT command for a view or materialized view,
working from a textual name for the view rather than its OID. (This is deprecated;
use the OID variant instead.)
pg_index_column_has_property
pg_index_column_has_property ( indexregclass,columninteger,property text ) → boolean
Tests whether an index column has the named property. Common index column properties are listed in table below. (Note that extension access methods can define additional property names for their indexes.) NULL is returned if the property name is not known or does not apply to the particular object, or if the OID or column number does not identify a valid object.
Index Column Properties
| Name | Description |
|---|---|
| asc | Does the column sort in ascending order on a forward scan? |
| desc | Does the column sort in descending order on a forward scan? |
| nulls_first | Does the column sort with nulls first on a forward scan? |
| nulls_last | Does the column sort with nulls last on a forward scan? |
| orderable | Does the column possess any defined sort ordering? |
| distance_orderable | Can the column be scanned in order by a “distance” operator, for example ORDER BY col <-> constant? |
| returnable | Can the column value be returned by an index-only scan? |
| search_array | Does the column natively support col = ANY(array) searches? |
| search_nulls | Does the column support IS NULL and IS NOT NULL searches? |
pg_index_has_property
pg_index_has_property ( indexregclass,property text ) → boolean
Tests whether an index has the named property. Common index properties are listed in table below. (Note that extension access methods can define additional property names for their indexes.) NULL is returned if the property name is not known or does not apply to the particular object, or if the OID does not identify a valid object.
Index Properties
| Name | Description |
|---|---|
| clusterable | Can the index be used in a CLUSTER command? |
| index_scan | Does the index support plain (non-bitmap) scans? |
| bitmap_scan | Does the index support bitmap scans? |
| backward_scan | Can the scan direction be changed in mid-scan (to support FETCH BACKWARD on a cursor without needing materialization)? |
pg_indexam_has_property
pg_indexam_has_property ( amoid,property text ) → boolean
Tests whether an index access method has the named property. Access method properties are listed in table below. NULL is returned if the property name is not known or does not apply to the particular object, or if the OID does not identify a valid object.
Index Access Method Properties
| Name | Description |
|---|---|
| can_order | Does the access method support ASC, DESC and related keywords in CREATE INDEX? |
| can_unique | Does the access method support unique indexes? |
| can_multi_col | Does the access method support indexes with multiple columns? |
| can_exclude | Does the access method support exclusion constraints? |
| can_include | Does the access method support the INCLUDE clause of CREATE INDEX? |
pg_options_to_table
pg_options_to_table ( options_arraytext[] ) → setof record (option_nametext,option_value text )
Returns the set of storage options represented by a value from pg_class.reloptions or pg_attribute.attoptions.
pg_settings_get_flags
pg_settings_get_flags ( guc text ) → text[]
Returns an array of the flags associated with the given GUC, or NULL if it does not exist. The result is an empty array if the GUC exists but there are no flags to show. Only the most useful flags listed in table below are exposed.
GUC Flags
| Flag | Description |
|---|---|
| EXPLAIN | Parameters with this flag are included in EXPLAIN (SETTINGS) commands. |
| NO_SHOW_ALL | Parameters with this flag are excluded from SHOW ALL commands. |
| NO_RESET_ALL | Parameters with this flag are excluded from RESET ALL commands. |
| NOT_IN_SAMPLE | Parameters with this flag are not included in qhb.conf by default. |
| RUNTIME_COMPUTED | Parameters with this flag are runtime-computed ones. |
pg_tablespace_databases
pg_tablespace_databases ( tablespace oid ) → setof oid
Returns the set of OIDs of databases that have objects stored in the specified tablespace. If this function returns any rows, the tablespace is not empty and cannot be dropped. To identify the specific objects populating the tablespace, you will need to connect to the database(s) identified by pg_tablespace_databases and query their pg_class catalogs.
pg_tablespace_location
pg_tablespace_location ( tablespace oid ) → text
Returns the file system path that this tablespace is located in.
pg_typeof
pg_typeof ( "any" ) → regtype
Returns the OID of the data type of the value that is passed to it. This can be helpful for troubleshooting or dynamically constructing SQL queries. The function is declared as returning regtype, which is an OID alias type (see Section Object Identifier Types); this means that it is the same as an OID for comparison purposes but displays as a type name.
For example:
SELECT pg_typeof(33);
pg_typeof
-----------
integer
SELECT typlen FROM pg_type WHERE oid = pg_typeof(33);
typlen
--------
4
COLLATION FOR
COLLATION FOR ( "any" ) → text
Returns the name of the collation of the value that is passed to it. The value is quoted and schema-qualified if necessary. If no collation was derived for the argument expression, then NULL is returned. If the argument is not of a collatable data type, then an error is raised.
For example:
SELECT collation for (description) FROM pg_description LIMIT 1;
pg_collation_for
------------------
"default"
SELECT collation for ('foo' COLLATE "de_DE");
pg_collation_for
------------------
"de_DE"
to_regclass
to_regclass ( text ) → regclass
Translates a textual relation name to its OID. A similar result is obtained by casting the string to type regclass (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regcollation
to_regcollation ( text ) → regcollation
Translates a textual collation name to its OID. A similar result is obtained by casting the string to type regcollation (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regnamespace
to_regnamespace ( text ) → regnamespace
Translates a textual schema name to its OID. A similar result is obtained by casting the string to type regnamespace (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regoper
to_regoper ( text ) → regoper
Translates a textual operator name to its OID. A similar result is obtained by casting the string to type regoper (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found or is ambiguous.
to_regoperator
to_regoperator ( text ) → regoperator
Translates a textual operator name (with parameter types) to its OID. A similar result is obtained by casting the string to type regoperator (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regproc
to_regproc ( text ) → regproc
Translates a textual function or procedure name to its OID. A similar result is obtained by casting the string to type regproc (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found or is ambiguous.
to_regprocedure
to_regprocedure ( text ) → regprocedure
Translates a textual function or procedure name (with argument types) to its OID. A similar result is obtained by casting the string to type regprocedure (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regrole
to_regrole ( text ) → regrole
Translates a textual role name to its OID. A similar result is obtained by casting the string to type regrole (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
to_regtype
to_regtype ( text ) → regtype
Translates a textual type name to its OID. A similar result is obtained by casting the string to type regtype (see Section Object Identifier Types); however, this function will return NULL rather than throwing an error if the name is not found.
Note
Most of the functions that reconstruct (decompile) database objects have an optional pretty flag, which if true causes the result to be “pretty-printed”. Pretty-printing suppresses unnecessary parentheses and adds whitespace for legibility. The pretty-printed format is more readable, but the default format is more likely to be interpreted the same way by future versions of QHB; so avoid using pretty-printed output for dump purposes. Passing false for the pretty parameter yields the same result as omitting the parameter.
Object Information and Addressing Functions
This section lists functions related to database object identification and addressing.
pg_describe_object
pg_describe_object ( classidoid,objidoid,objsubid integer ) → text
Returns a textual description of a database object identified by catalog OID, object OID, and sub-object ID (such as a column number within a table; the sub- object ID is zero when referring to a whole object). This description is intended to be human-readable, and might be translated, depending on server configuration. This is especially useful to determine the identity of an object referenced in the pg_depend catalog. This function returns NULL values for undefined objects.
pg_identify_object
pg_identify_object ( classidoid,objidoid,objsubidinteger ) → record (typetext,schematext,nametext,identity text )
Returns a row containing enough information to uniquely identify the database object specified by catalog OID, object OID and sub-object ID. This information is intended to be machine-readable, and is never translated. type identifies the type of database object; schema is the schema name that the object belongs in, or NULL for object types that do not belong to schemas; name is the name of the object, quoted if necessary, if the name (along with schema name, if pertinent) is sufficient to uniquely identify the object, otherwise NULL; identity is the complete object identity, with the precise format depending on object type, and each name within the format being schema-qualified and quoted as necessary. Undefined objects are identified with NULL values.
pg_identify_object_as_address
pg_identify_object_as_address ( classidoid,objidoid,objsubidinteger ) → record (typetext,object_namestext[],object_args text[] )
Returns a row containing enough information to uniquely identify the database object specified by catalog OID, object OID and sub-object ID. The returned information is independent of the current server, that is, it could be used to identify an identically named object in another server. type identifies the type of database object; object_names and object_args are text arrays that together form a reference to the object. These three values can be passed to pg_get_object_address to obtain the internal address of the object.
pg_get_object_address
pg_get_object_address ( typetext,object_namestext[],object_argstext[] ) → record (classidoid,objidoid,objsubid integer )
Returns a row containing enough information to uniquely identify the database object specified by a type code and object name and argument arrays. The returned values are the ones that would be used in system catalogs such as pg_depend; they can be passed to other system functions such as pg_describe_object or pg_identify_object. classid is the OID of the system catalog containing the object; objid is the OID of the object itself, and objsubid is the sub-object ID, or zero if none. This function is the inverse of pg_identify_object_as_address. Undefined objects are identified with NULL values.
Comment Information Functions
The functions shown in this section extract comments previously stored with the COMMENT command. A null value is returned if no comment could be found for the specified parameters.
col_description
col_description ( tableoid,column integer ) → text
Returns the comment for a table column, which is specified by the OID of its table and its column number. (obj_description cannot be used for table columns, since columns do not have OIDs of their own.)
obj_description
obj_description ( objectoid,catalog name ) → text
Returns the comment for a database object specified by its OID and the name of
the containing system catalog. For example obj_description(123456, 'pg_class')
would retrieve the comment for the table with OID 123456.
obj_description ( object oid ) → text
Returns the comment for a database object specified by its OID alone. This is deprecated since there is no guarantee that OIDs are unique across different system catalogs; therefore, the wrong comment might be returned.
shobj_description
shobj_description ( objectoid,catalog name ) → text
Returns the comment for a shared database object specified by its OID and the name of the containing system catalog. This is just like obj_description except that it is used for retrieving comments on shared objects (that is, databases, roles, and tablespaces). Some system catalogs are global to all databases within each cluster, and the descriptions for objects in them are stored globally as well.
Data Validity Checking Functions
The functions shown in this section can be helpful for checking validity of proposed input data.
pg_input_is_valid
pg_input_is_valid ( stringtext,type text ) → boolean
Tests whether the given string is valid input for the specified data type,
returning true or false.
This function will only work as desired if the data type's input function has
been updated to report invalid input as a “soft” error. Otherwise, invalid input
will abort the transaction, just as if the string had been cast to the type
directly.
pg_input_is_valid('42', 'integer') → t
pg_input_is_valid('42000000000', 'integer') → f
pg_input_is_valid('1234.567', 'numeric(7,4)') → f
pg_input_error_info
pg_input_error_info ( stringtext,typetext ) → record (messagetext,detailtext,hinttext,sql_error_code text )
Tests whether the given string is valid input for the specified data type;
if not, return the details of the error that would have been thrown. If the input
is valid, the results are NULL. The inputs are the same as for pg_input_is_valid.
This function will only work as desired if the data type's input function has
been updated to report invalid input as a “soft” error. Otherwise, invalid input
will abort the transaction, just as if the string had been cast to the type
directly.
select * from pg_input_error_info('42000000000', 'integer') →
message | detail | hint | sql_error_code
------------------------------------------------------+--------+------+----------------
value "42000000000" is out of range for type integer | | | 22003
select message, detail from pg_input_error_info('1234.567', 'numeric(7,4)') →
message | detail
------------------------+-----------------------------------------------------------------------------------
numeric field overflow | A field with precision 7, scale 4 must round to an absolute value less than 10^3.
Transaction ID and Snapshot Information Functions
The functions shown in this section provide server transaction information in an exportable form. The main use of these functions is to determine which transactions were committed between two snapshots.
age
age ( xid ) → integer
Returns the number of transactions between the supplied transaction id and the current transaction counter.
mxid_age
mxid_age ( xid ) → integer
Returns the number of multixacts IDs between the supplied multixact ID and the current multixacts counter.
pg_current_xact_id
pg_current_xact_id () → xid8
Returns the current transaction's ID. It will assign a new one if the current transaction does not have one already (because it has not performed any database updates); see Section Transactions and Identifiers for details. If executed in a subtransaction, this will return the top-level transaction ID; see Section Subtransactions for details.
pg_current_xact_id_if_assigned
pg_current_xact_id_if_assigned () → xid8
Returns the current transaction's ID, or NULL if no ID is assigned yet. (It's best to use this variant if the transaction might otherwise be read-only, to avoid unnecessary consumption of an XID.) If executed in a subtransaction, this will return the top-level transaction ID.
pg_xact_status
pg_xact_status ( xid8 ) → text
Reports the commit status of a recent transaction. The result is one of in progress,
committed, or aborted, provided that the transaction is recent enough that
the system retains the commit status of that transaction. If it is old enough
that no references to the transaction survive in the system and the commit status
information has been discarded, the result is NULL. Applications might use this
function, for example, to determine whether their transaction committed or aborted
after the application and database server become disconnected while a COMMIT is
in progress. Note that prepared transactions are reported as in progress;
applications must check pg_prepared_xacts if they need to determine whether
a transaction ID belongs to a prepared transaction.
pg_current_snapshot
pg_current_snapshot () → pg_snapshot
Returns a current snapshot, a data structure showing which transaction IDs are now in-progress. Only top-level transaction IDs are included in the snapshot; subtransaction IDs are not shown; see Section Subtransactions for details.
pg_snapshot_xip
pg_snapshot_xip ( pg_snapshot ) → setof xid8
Returns the set of in-progress transaction IDs contained in a snapshot.
pg_snapshot_xmax
pg_snapshot_xmax ( pg_snapshot ) → xid8
Returns the xmax of a snapshot.
pg_snapshot_xmin
pg_snapshot_xmin ( pg_snapshot ) → xid8
Returns the xmin of a snapshot.
pg_visible_in_snapshot
pg_visible_in_snapshot ( xid8, pg_snapshot ) → boolean
Is the given transaction ID visible according to this snapshot (that is, was it completed before the snapshot was taken)? Note that this function will not give the correct answer for a subtransaction ID (subxid); see Section Subtransactions for details.
Note
The internal transaction ID type xid is 32 bits wide and wraps around every 4
billion transactions. However, the functions shown in this section, except age, and
mxid_age, use a 64-bit type xid8 that does
not wrap around during the life of an installation, and can be converted to xid
by casting if required; see Section Transactions and Identifiers for details.
The data type pg_snapshot stores information about transaction ID visibility
at a particular moment in time. Its components are described in section below.
pg_snapshot's textual representation is xmin:xmax:xip_list. For example
10:20:10,14,15 means xmin=10, xmax=20, xip_list=10, 14, 15.
Snapshot Components
| Name | Description |
|---|---|
| xmin | Lowest transaction ID that was still active. All transaction IDs less than xmin are either committed and visible, or rolled back and dead. |
| xmax | One past the highest completed transaction ID. All transaction IDs greater than or equal to xmax had not yet completed as of the time of the snapshot, and thus are invisible. |
| xip_list | Transactions in progress at the time of the snapshot. A transaction ID that is xmin <= id < xmax and not in this list was already completed at the time of the snapshot, and thus is either visible or dead according to its commit status. This list does not include the transaction IDs of subtransactions (subxids). |
Deprecated Transaction ID and Snapshot Information Functions
In releases of QHB before 1.5.1 there was no xid8 type, so variants of these functions were provided that used bigint to represent a 64-bit XID, with a correspondingly distinct snapshot data type txid_snapshot. These older functions have txid in their names. They are still supported for backward compatibility, but may be removed from a future release. See below.
txid_current
txid_current () → bigint
See pg_current_xact_id().
txid_current_if_assigned
txid_current_if_assigned () → bigint
See pg_current_xact_id_if_assigned().
txid_current_snapshot
txid_current_snapshot () → txid_snapshot
See pg_current_snapshot().
txid_snapshot_xip
txid_snapshot_xip ( txid_snapshot ) → setof bigint
See pg_snapshot_xip().
txid_snapshot_xmax
txid_snapshot_xmax ( txid_snapshot ) → bigint
See pg_snapshot_xmax().
txid_snapshot_xmin
txid_snapshot_xmin ( txid_snapshot ) → bigint
See pg_snapshot_xmin().
txid_visible_in_snapshot
txid_visible_in_snapshot ( bigint, txid_snapshot ) → boolean
See pg_visible_in_snapshot().
txid_status
txid_status ( bigint ) → text
See pg_xact_status().
Committed Transaction Information Functions
The functions shown in this section provide information about when past transactions were committed. They only provide useful data when the track_commit_timestamp configuration option is enabled, and only for transactions that were committed after it was enabled. Commit timestamp information is routinely removed during vacuum.
pg_xact_commit_timestamp
pg_xact_commit_timestamp ( xid ) → timestamp with time zone
Returns the commit timestamp of a transaction.
pg_xact_commit_timestamp_origin
pg_xact_commit_timestamp_origin ( xid ) → record ( timestamptimestamp with time zone,roident oid)
Returns the commit timestamp and replication origin of a transaction.
pg_last_committed_xact
pg_last_committed_xact () → record ( xidxid,timestamptimestamp with time zone,roident oid )
Returns the transaction ID, commit timestamp and replication origin of the latest committed transaction.
Control Data Functions
The functions shown in this section print information initialized during qhb_bootstrap (or initdb), such as the catalog version. They also show information about write-ahead logging and checkpoint processing. This information is cluster-wide, not specific to any one database. These functions provide most of the same information, from the same source, as the qhb_controldata application.
pg_control_checkpoint
pg_control_checkpoint () → record
Returns information about current checkpoint state, as shown in table below.
pg_control_checkpoint Output Columns
| Column Name | Data Type |
|---|---|
| checkpoint_lsn | pg_lsn |
| redo_lsn | pg_lsn |
| redo_wal_file | text |
| timeline_id | integer |
| prev_timeline_id | integer |
| full_page_writes | boolean |
| next_xid | text |
| next_oid | oid |
| next_multixact_id | xid |
| next_multi_offset | xid |
| oldest_xid | xid |
| oldest_xid_dbid | oid |
| oldest_active_xid | xid |
| oldest_multi_xid | xid |
| oldest_multi_dbid | oid |
| oldest_commit_ts_xid | xid |
| newest_commit_ts_xid | xid |
| checkpoint_time | timestamp with time zone |
pg_control_system
pg_control_system () → record
Returns information about current control file state, as shown in table below.
pg_control_system Output Columns
| Column Name | Data Type |
|---|---|
| pg_control_version | integer |
| catalog_version_no | integer |
| system_identifier | bigint |
| pg_control_last_modified | timestamp with time zone |
pg_control_init
pg_control_init () → record
Returns information about cluster initialization state, as shown in table below.
pg_control_init Output Columns
| Column Name | Data Type |
|---|---|
| max_data_alignment | integer |
| database_block_size | integer |
| blocks_per_segment | integer |
| wal_block_size | integer |
| bytes_per_wal_segment | integer |
| max_identifier_length | integer |
| max_index_columns | integer |
| max_toast_chunk_size | integer |
| large_object_chunk_size | integer |
| float8_pass_by_value | boolean |
| data_page_checksum_version | integer |
pg_control_recovery
pg_control_recovery () → record
Returns information about recovery state, as shown in table below.
pg_control_recovery Output Columns
| Column Name | Data Type |
|---|---|
| min_recovery_end_lsn | pg_lsn |
| min_recovery_end_timeline | integer |
| backup_start_lsn | pg_lsn |
| backup_end_lsn | pg_lsn |
| end_of_backup_record_required | boolean |