Date: Mon, 27 Nov 2017 07:33:38 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: pgsql-hackers@postgresql.org
Subject: Re: PG10.1 autovac killed building extended stats
Message-ID: <20171127133338.GC19405@telsasoft.com>
References: <20171117152714.GA25754@telsasoft.com>
 <20171117163600.d7zsm2odaizikdhs@alvherre.pgsql>
 <20171117214352.GE25796@telsasoft.com>
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On Fri, Nov 17, 2017 at 03:43:52PM -0600, Justin Pryzby wrote:
> On Fri, Nov 17, 2017 at 01:36:00PM -0300, Alvaro Herrera wrote:
> > Justin Pryzby wrote:
> > 
> > > Core was generated by `postgres: autovacuum worker process   gtt             '.
> > > Program terminated with signal 11, Segmentation fault.
> > > #0  statext_ndistinct_build (totalrows=300, numrows=300, rows=0x21df3e8, attrs=<value optimized out>, stats=0x0) at mvdistinct.c:103
> > > 103                                     item->attrs = bms_add_member(item->attrs,
> > > 
> > > (gdb) p stats
> > > $5 = (VacAttrStats **) 0x0
> > > => This is an error, no ??
> > 
> > Not necessarily, but then I think this previous code is busted:
> 
> > If I recall things correctly, the "continue" should be executed
> > regardless of IsAutoVacuumWorkerProcess() (only the log should be
> > conditional on that).  I'm not sure how I arrived at the current coding,
> > which I added in bf2a691e02d7 -- probably just fuzzy thinking.
> 
> Is it useful to run with that change ?

FYI: the affected server ran without crashing since Nov 18 with this change.

--- postgresql-10.1.orig/src/backend/statistics/extended_stats.c	2017-11-06 20:46:52.000000000 -0400
+++ postgresql-10.1/src/backend/statistics/extended_stats.c	2017-11-18 18:23:44.057988419 -0400
@@ -98,20 +98,21 @@
 		if (!stats && !IsAutoVacuumWorkerProcess())
 		{
 			ereport(WARNING,
 					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 					 errmsg("statistics object \"%s.%s\" could not be computed for relation \"%s.%s\"",
 							stat->schema, stat->name,
 							get_namespace_name(onerel->rd_rel->relnamespace),
 							RelationGetRelationName(onerel)),
 					 errtable(onerel)));
-			continue;
 		}
+		if (!stats)
+			continue;
 
 		/* check allowed number of dimensions */
 		Assert(bms_num_members(stat->columns) >= 2 &&
 			   bms_num_members(stat->columns) <= STATS_MAX_DIMENSIONS);
 
 		/* compute statistic of each requested type */
 		foreach(lc2, stat->types)
 		{
 			char		t = (char) lfirst_int(lc2);

Justin

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--- postgresql-10.1.orig/src/backend/statistics/extended_stats.c	2017-11-06 20:46:52.000000000 -0400
+++ postgresql-10.1/src/backend/statistics/extended_stats.c	2017-11-18 18:23:44.057988419 -0400
@@ -98,20 +98,21 @@
 		if (!stats && !IsAutoVacuumWorkerProcess())
 		{
 			ereport(WARNING,
 					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 					 errmsg("statistics object \"%s.%s\" could not be computed for relation \"%s.%s\"",
 							stat->schema, stat->name,
 							get_namespace_name(onerel->rd_rel->relnamespace),
 							RelationGetRelationName(onerel)),
 					 errtable(onerel)));
-			continue;
 		}
+		if (!stats)
+			continue;
 
 		/* check allowed number of dimensions */
 		Assert(bms_num_members(stat->columns) >= 2 &&
 			   bms_num_members(stat->columns) <= STATS_MAX_DIMENSIONS);
 
 		/* compute statistic of each requested type */
 		foreach(lc2, stat->types)
 		{
 			char		t = (char) lfirst_int(lc2);

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