Chapter 47. libpq C++ Binding

Table of Contents
Control and Initialization
libpq++ Classes
Database Connection Functions
Query Execution Functions
Asynchronous Notification
Functions Associated with the COPY Command
Caveats

libpq++ is the C++ API to Postgres. libpq++ is a set of classes which allow client programs to connect to the Postgres backend server. These connections come in two forms: a Database Class and a Large Object class.

The Database Class is intended for manipulating a database. You can send all sorts of SQL queries to the Postgres backend server and retrieve the responses of the server.

The Large Object Class is intended for manipulating a large object in a database. Although a Large Object instance can send normal queries to the Postgres backend server it is only intended for simple queries that do not return any data. A large object should be seen as a file stream. In the future it should behave much like the C++ file streams cin, cout and cerr.

This chapter is based on the documentation for the libpq C library. Three short programs are listed at the end of this section as examples of libpq++ programming (though not necessarily of good programming). There are several examples of libpq++ applications in src/libpq++/examples, including the source code for the three examples in this chapter.

Control and Initialization

Environment Variables

The following environment variables can be used to set up default values for an environment and to avoid hard-coding database names into an application program:

Note: Refer to the libpq for a complete list of available connection options.

The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb or PQsetdbLogin if no value is directly specified by the calling code. These are useful to avoid hard-coding database names into simple application programs.

Note: libpq++ uses only environment variables or PQconnectdb conninfo style strings.

The following environment variables can be used to specify user-level default behavior for every Postgres session:

The following environment variables can be used to specify default internal behavior for every Postgres session:

Refer to the SET SQL command for information on correct values for these environment variables.