On Mon, 2007-02-05 at 11:55 +0000, Simon Riggs wrote:
> On Sat, 2007-02-03 at 22:11 -0500, Bruce Momjian wrote:
> > Tom Lane wrote:
> > > Peter Eisentraut <[EMAIL PROTECTED]> writes:
> > > > vacuumlazy.c contains a hint "Consider compacting this relation" but
> > > > AFAICT,
> > > > there is no indication anywhere how "compacting" is supposed to be
> > > > achieved.
> > > > I guess this means VACUUM FULL or CLUSTER, but I don't think the hint
> > > > can be
> > > > processed effectively by a user.
> > >
> > > So change it ...
> >
> > New message is:
> >
> > errhint("Consider using VACUUM FULL on this relation or increasing the
> > configuration parameter \"max_fsm_pages\".")));
> >
>
> The change of wording may be appropriate, but it is triggered when
>
> if (vacrelstats->tot_free_pages > MaxFSMPages)
>
> So if you VACUUM a 15+GB table and it has only 1% freespace then it will
> still generate this message. Hopefully you'd agree that the message
> would be inappropriate in that case.
>
> It's also inappropriate because this message is generated *prior* to
> doing lazy_truncate_heap(), which could easily remove lots of empty
> pages anyhow. That might reduce it to less than MaxFSMPages anyhow, so
> it can currently be triggered in wholly inappropriate situations.
>
> So I suggest that we move this wording after lazy_truncate_heap() in
> lazy_vacuum_rel() *and* we alter the hint so that it only suggests
> VACUUM FULL if the table has 20% fragmentation, whatever its size.
>
> Happy to drop a patch for this, if people agree.
Enclose 2 versions:
v1 - move test and WARNING
v2 - move test and WARNING, plus adjust hint according to relation size
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
Index: src/backend/commands/vacuumlazy.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v
retrieving revision 1.83
diff -c -r1.83 vacuumlazy.c
*** src/backend/commands/vacuumlazy.c 4 Feb 2007 03:10:55 -0000 1.83
--- src/backend/commands/vacuumlazy.c 5 Feb 2007 17:19:55 -0000
***************
*** 180,185 ****
--- 180,192 ----
/* Update shared free space map with final free space info */
lazy_update_fsm(onerel, vacrelstats);
+ if (vacrelstats->tot_free_pages > MaxFSMPages)
+ ereport(WARNING,
+ (errmsg("relation \"%s.%s\" contains more than \"max_fsm_pages\" pages with useful free space",
+ get_namespace_name(RelationGetNamespace(onerel)),
+ RelationGetRelationName(onerel)),
+ errhint("Consider using VACUUM FULL on this relation or increasing the configuration parameter \"max_fsm_pages\".")));
+
/* Update statistics in pg_class */
vac_update_relstats(RelationGetRelid(onerel),
vacrelstats->rel_pages,
***************
*** 507,519 ****
vacrelstats->tot_free_pages,
empty_pages,
pg_rusage_show(&ru0))));
-
- if (vacrelstats->tot_free_pages > MaxFSMPages)
- ereport(WARNING,
- (errmsg("relation \"%s.%s\" contains more than \"max_fsm_pages\" pages with useful free space",
- get_namespace_name(RelationGetNamespace(onerel)),
- relname),
- errhint("Consider using VACUUM FULL on this relation or increasing the configuration parameter \"max_fsm_pages\".")));
}
--- 514,519 ----
Index: src/backend/commands/vacuumlazy.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v
retrieving revision 1.83
diff -c -r1.83 vacuumlazy.c
*** src/backend/commands/vacuumlazy.c 4 Feb 2007 03:10:55 -0000 1.83
--- src/backend/commands/vacuumlazy.c 5 Feb 2007 17:10:16 -0000
***************
*** 66,71 ****
--- 66,73 ----
#define REL_TRUNCATE_MINIMUM 1000
#define REL_TRUNCATE_FRACTION 16
+ /* multiplier for acceptable fragmentation before WARNING */
+ #define REL_FRAGMENTATION_FACTOR 5
typedef struct LVRelStats
{
***************
*** 180,185 ****
--- 182,196 ----
/* Update shared free space map with final free space info */
lazy_update_fsm(onerel, vacrelstats);
+ if (vacrelstats->tot_free_pages > MaxFSMPages)
+ ereport(WARNING,
+ (errmsg("relation \"%s.%s\" contains more than \"max_fsm_pages\" pages with useful free space",
+ get_namespace_name(RelationGetNamespace(onerel)),
+ RelationGetRelationName(onerel)),
+ errhint("Consider%sincreasing the configuration parameter \"max_fsm_pages\".",
+ (REL_FRAGMENTATION_FACTOR * vacrelstats->tot_free_pages > vacrelstats->rel_pages
+ ? " using VACUUM FULL on this relation or ": " "))));
+
/* Update statistics in pg_class */
vac_update_relstats(RelationGetRelid(onerel),
vacrelstats->rel_pages,
***************
*** 507,519 ****
vacrelstats->tot_free_pages,
empty_pages,
pg_rusage_show(&ru0))));
-
- if (vacrelstats->tot_free_pages > MaxFSMPages)
- ereport(WARNING,
- (errmsg("relation \"%s.%s\" contains more than \"max_fsm_pages\" pages with useful free space",
- get_namespace_name(RelationGetNamespace(onerel)),
- relname),
- errhint("Consider using VACUUM FULL on this relation or increasing the configuration parameter \"max_fsm_pages\".")));
}
--- 518,523 ----
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