pg_self_query is based on the pg_query_state extension and is necessary for one purpose - to receive the current (not the top level like current_query()) query for saving it in the audit subsystem (in audit triggers).

The pg_self_query function does not accept any parameters, since it is called only for the current PID. Also, unlike pg_query_state, it does not return anything except the frame number and the query text (previous frame from the current one) for writing to the log. Thus, it is easy to capture a query text, which actually changes the data in tables. So, you can use this function in your audit triggers.

Before using this extension, you must first install the pg_query_state extension, which adds the necessary hooks to intercept query state.

Using this module there can help in the following things:

• log (in audit triggers) queries, which actually changes the data in tables

To install pg_self_query, please apply corresponding patches runtime_explain.patch (or runtime_explain_11.0.patch for PG11) from pg_query_state extension to reqired stable version of PostgreSQL and rebuild PostgreSQL.

Then execute this in the module's directory:

make install USE_PGXS=1

It is essential to restart the PostgreSQL instance. After that, execute the following query in psql:

CREATE EXTENSION pg_self_query;

Done!

pg_self_query()
	returns TABLE ( frame_number integer,
	                query_text text)

Extract current query state from the current pid.