Re: memory leak in postgresql

Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> I found a following issue (tested on PostgreSQL 9.2)

> CREATE OR REPLACE FUNCTION public.setfield(a anyelement, text, text)
> RETURNS anyelement
> LANGUAGE plpgsql
> AS $function$
> begin
> create temp table aux as select $1.*;
> execute 'update aux set ' || quote_ident($2) || ' = ' || quote_literal($3);
> select into $1 * from aux;
> drop table aux;
> return $1;
> end;
> $function$

> create type mypoint as (a int, b int);

> create table omega(p mypoint);

> insert into omega select mypoint '(10,20)' from generate_series(1,100000);

> update omega set p = setfield(p, 'a', '20');

> WARNING: out of shared memory
> CONTEXT: SQL statement "create temp table aux as select $1.*"
> PL/pgSQL function "setfield" line 3 at SQL statement
> ERROR: out of shared memory
> HINT: You might need to increase max_locks_per_transaction.
> CONTEXT: SQL statement "create temp table aux as select $1.*"
> PL/pgSQL function "setfield" line 3 at SQL statement

This is not a memory leak, this is a "your transaction is holding too
many locks" problem (namely, one lock for each transient table). Please
follow the advice given in the error message.

regards, tom lane