PostgreSQL, Pl/pgsql - How to access a query string that executed the stored procedure i'm in?

Question

is there a way to access the query string from within a stored procedure? i mean i'd like to add some debugging to a lot of stored procedures and it would be brilliant if i had some constant accessible from the body of the procedure, which had the query string.

something which would work with EXECUTE.

i've read the docs and cannot see anything like that...

thanks!

Answer 1

I agree with Pavel that your requirement is not real clear. However, I guess that you want the to get the statement that called the procedure currently running. If so then there may be a built in function: Current_Query(). Following is an example of its use.

 create or replace function what_called_me()
    returns text
    language sql
  as $$
      select current_query();
  $$; 

  select 1 num, 'A' col, what_called_me() sql_statement;   

Answer 2

I don't understand well, what you need, but maybe you need plpgsql plugin API. This API is not well documented, but there is lot of PostgreSQL extensions that use this API - PLdebugger, plpgsql_chec, plprofiler and maybe other.

/*
 * A PLpgSQL_plugin structure represents an instrumentation plugin.
 * To instrument PL/pgSQL, a plugin library must access the rendezvous
 * variable "PLpgSQL_plugin" and set it to point to a PLpgSQL_plugin struct.
 * Typically the struct could just be static data in the plugin library.
 * We expect that a plugin would do this at library load time (_PG_init()).
 * It must also be careful to set the rendezvous variable back to NULL
 * if it is unloaded (_PG_fini()).
 *
 * This structure is basically a collection of function pointers --- at
 * various interesting points in pl_exec.c, we call these functions
 * (if the pointers are non-NULL) to give the plugin a chance to watch
 * what we are doing.
 *
 * func_setup is called when we start a function, before we've initialized
 * the local variables defined by the function.
 *
 * func_beg is called when we start a function, after we've initialized
 * the local variables.
 *
 * func_end is called at the end of a function.
 *
 * stmt_beg and stmt_end are called before and after (respectively) each
 * statement.
 *
 * Also, immediately before any call to func_setup, PL/pgSQL fills in the
 * error_callback and assign_expr fields with pointers to its own
 * plpgsql_exec_error_callback and exec_assign_expr functions.  This is
 * a somewhat ad-hoc expedient to simplify life for debugger plugins.
 */
typedef struct PLpgSQL_plugin
{
    /* Function pointers set up by the plugin */
    void        (*func_setup) (PLpgSQL_execstate *estate, PLpgSQL_function *func);
    void        (*func_beg) (PLpgSQL_execstate *estate, PLpgSQL_function *func);
    void        (*func_end) (PLpgSQL_execstate *estate, PLpgSQL_function *func);
    void        (*stmt_beg) (PLpgSQL_execstate *estate, PLpgSQL_stmt *stmt);
    void        (*stmt_end) (PLpgSQL_execstate *estate, PLpgSQL_stmt *stmt);

    /* Function pointers set by PL/pgSQL itself */
    void        (*error_callback) (void *arg);
    void        (*assign_expr) (PLpgSQL_execstate *estate, PLpgSQL_datum *target,
                                PLpgSQL_expr *expr);
} PLpgSQL_plugin;

This is necessary when you really need to detail info about what is inside.

Maybe you need information just about executed queries - then you can look on extension auto_explain , when you set auto_explain.log_nested_statements to on , then the queries from procedure will be logged.