Chapter 5. libpgeasy - Simplified C Library

pgeasy allows you to cleanly interface to the libpq library, more like a 4GL SQL interface. Refer to Chapter 1 for more information about libpq

It consists of set of simplified C functions that encapsulate the functionality of libpq. The functions are:

• PGresult   *doquery(char *query);

• PGconn     *connectdb(char *options);

• void        disconnectdb();

• int         fetch(void *param,...);

• int         fetchwithnulls(void *param,...);

• void        reset_fetch();

• void        on_error_continue();

• void        on_error_stop();

• PGresult   *get_result();

• void        set_result(PGresult *newres);

• void        unset_result(PGresult *oldres);

Many functions return a structure or value, so you can do more work with the result if required.

You basically connect to the database with connectdb, issue your query with doquery, fetch the results with fetch, and finish with disconnectdb.

For SELECT queries, fetch allows you to pass pointers as parameters, and on return the variables are filled with data from the binary cursor you opened. These binary cursors cannot be used if you are running the pgeasy client on a system with a different architecture than the database server. If you pass a NULL pointer parameter, the column is skipped. fetchwithnulls allows you to retrieve the NULL status of the field by passing an int* after each result pointer, which returns true or false if the field is null. You can always use libpq functions on the PGresult pointer returned by doquery. reset_fetch starts the fetch back at the beginning.

get_result, set_result, and unset_result allow you to handle multiple result sets at the same time.

There are several demonstration programs in the source directory.