On 02/03/2014 09:09 AM, Craig Ringer wrote: > At a guess, we're looking at a case where a new child context is created > at every call, so every MemoryContextResetChildren call has to deal with > more child contexts.
That would be "yes". After a short run, I see 32849 lines like: json_array_elements temporary cxt: 8192 total in 1 blocks; 8160 free (0 chunks); 32 used under the context: PortalMemory: 8192 total in 1 blocks PortalHeapMemory: 7168 total in 3 blocks ExecutorState: 65600 total in 4 blocks ExprContext: 8192 total in 1 blocks json_array_elements temporary cxt: 8192 total in 1 blocks; 8160 free (0 chunks); 32 used The attached patch deletes the context after use, bringing performance back into line. It should be backpatched to 9.3. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
>From f4ae516d643dee43200053533dbcc8b362e3f92b Mon Sep 17 00:00:00 2001 From: Craig Ringer <cr...@2ndquadrant.com> Date: Mon, 3 Feb 2014 09:47:34 +0800 Subject: [PATCH] Fix leaked memory context in json_array_each and json_each json_array_each and json_each leaked a memory context with each invocation, causing profiles involving many invocations in a single query context to be dominated by MemoryContextReset because of MemoryContextResetChildren calls made after each tuple is emitted. See initial bug report: http://stackoverflow.com/q/21507127/398670 and list discussion: http://www.postgresql.org/message-id/52eeec37.9040...@2ndquadrant.com --- src/backend/utils/adt/jsonfuncs.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c index a19b222..116d7a0 100644 --- a/src/backend/utils/adt/jsonfuncs.c +++ b/src/backend/utils/adt/jsonfuncs.c @@ -975,6 +975,9 @@ each_worker(PG_FUNCTION_ARGS, bool as_text) rsi->setResult = state->tuple_store; rsi->setDesc = state->ret_tdesc; + MemoryContextDelete(state->tmp_cxt); + state->tmp_cxt = NULL; + PG_RETURN_NULL(); } @@ -1157,6 +1160,9 @@ elements_worker(PG_FUNCTION_ARGS, bool as_text) rsi->setResult = state->tuple_store; rsi->setDesc = state->ret_tdesc; + MemoryContextDelete(state->tmp_cxt); + state->tmp_cxt = NULL; + PG_RETURN_NULL(); } -- 1.8.3.1
-- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers