libpq — C Library

libpq is the C application programmer's interface to QHB. libpq is a set of library functions that allow client programs to pass queries to the QHB backend server and to receive the results of these queries.

libpq is also the underlying engine for several other QHB application interfaces, including those written for C++, Perl, Python, Tcl and ECPG. So some aspects of libpq's behavior will be important to you if you use one of those packages. In particular, Section Environment Variables, Section The Password File and Section SSL Support describe behavior that is visible to the user of any application that uses libpq.

Some short programs are included at the end of this chapter (Section Example Programs) to show how to write programs that use libpq.

Client programs that use libpq must include the header file libpq-fe.h and must link with the libpq library.

Table of Contents

• Database Connection Control Functions
  • Connection Strings
  • Parameter Key Words
• Connection Status Functions
• Command Execution Functions
  • Main Functions
  • Retrieving Query Result Information
  • Retrieving Other Result Information
  • Escaping Strings for Inclusion in SQL Commands
• Asynchronous Command Processing
• Pipeline Mode
  • Using Pipeline Mode
  • Functions Associated with Pipeline Mode
  • When to Use Pipeline Mode
• Retrieving Query Results Row-by-Row
• Canceling Queries in Progress
• The Fast-Path Interface
• Asynchronous Notification
• Functions Associated with the COPY Command
  • Functions for Sending COPY Data
  • Functions for Receiving COPY Data
  • Obsolete Functions for COPY
• Control Functions
• Miscellaneous Functions
• Notice Processing
• Event System
  • Event Types
  • Event Callback Procedure
  • Event Support Functions
  • Event Example
• Environment Variables
• The Password File
• The Connection Service File
• LDAP Lookup of Connection Parameters
• SSL Support
  • Client Verification of Server Certificates
  • Client Certificates
  • Protection Provided in Different Modes
  • SSL Client File Usage
  • SSL Library Initialization
• Behavior in Threaded Programs
• Building libpq Programs
• Example Programs