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Re: [COMMITTERS] pgsql: Reduce WAL activity for page splits: > Currently, an index split

From: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
To: Bruce Momjian <momjian(at)postgresql(dot)org>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [COMMITTERS] pgsql: Reduce WAL activity for page splits: > Currently, an index split
Date: 2007-02-08 08:31:28
Message-ID: 45CADFE0.4010001@kaltenbrunner.cc (view raw, whole thread or download thread mbox)
Thread:
Lists: pgsql-committerspgsql-hackers
Bruce Momjian wrote:
> Log Message:
> -----------
> Reduce WAL activity for page splits:
> 
>> Currently, an index split writes all the data on the split page to
>> WAL. That's a lot of WAL traffic. The tuples that are copied to the
>> right page need to be WAL logged, but the tuples that stay on the
>> original page don't.


this patch killed both of my OpenBSD buildfarm members

a backtrace of the crash shows:

(gdb) bt
#0  0x1c055504 in _bt_split (rel=0x835fcab0, buf=53, firstright=50, 
newitemoff=54, newitemsz=76,
     newitem=0x8210a364, newitemonleft=0 '\0') at nbtinsert.c:956
#1  0x1c05468b in _bt_insertonpg (rel=0x835fcab0, buf=53, 
stack=0x8210a078, keysz=2, scankey=0x8210a3f0,
     itup=0x8210a364, afteritem=0, split_only_page=0 '\0') at 
nbtinsert.c:538
#2  0x1c053fae in _bt_doinsert (rel=0x835fcab0, itup=0x8210a364, 
index_is_unique=1 '\001', heapRel=0x7ec0ee7c)
     at nbtinsert.c:141
#3  0x1c05a1c4 in btinsert (fcinfo=0x2) at nbtree.c:224
#4  0x1c2028fc in FunctionCall6 (flinfo=0x8bc6d1f0, arg1=2, arg2=2, 
arg3=2, arg4=2, arg5=2, arg6=2) at fmgr.c:1267
#5  0x1c052d20 in index_insert (indexRelation=0x835fcab0, 
values=0xcf7defd0, isnull=0xcf7df050 "",
     heap_t_ctid=0x7df53e50, heapRelation=0x7ec0ee7c, check_uniqueness=1 
'\001') at indexam.c:196
#6  0x1c08f87e in CatalogIndexInsert (indstate=0x2, 
heapTuple=0x8210a224) at indexing.c:124
#7  0x1c08f902 in CatalogUpdateIndexes (heapRel=0x7ec0ee7c, 
heapTuple=0x7df53e4c) at indexing.c:149
#8  0x1c17255c in SetRelationRuleStatus (relationId=10951, relHasRules=1 
'\001', relIsBecomingView=0 '\0')
     at rewriteSupport.c:80
#9  0x1c16f074 in DefineQueryRewrite (stmt=0x82ca7e78) at 
rewriteDefine.c:432
#10 0x1c18c822 in PortalRunUtility (portal=0x82cb201c, query=0x81897484, 
dest=0x3c0c8ff4,
     completionTag=0xcf7df2a0 "") at pquery.c:1063
#11 0x1c18cb12 in PortalRunMulti (portal=0x82cb201c, dest=0x3c0c8ff4, 
altdest=0x3c0c8ff4,
     completionTag=0xcf7df2a0 "") at pquery.c:1131
#12 0x1c18c28a in PortalRun (portal=0x82cb201c, count=2147483647, 
dest=0x3c0c8ff4, altdest=0x3c0c8ff4,
     completionTag=0xcf7df2a0 "") at pquery.c:700
#13 0x1c187d13 in exec_simple_query (
     query_string=0x84a2501c "/*\n * PostgreSQL System Views\n *\n * 
Copyright (c) 1996-2007, PostgreSQL Global Development Group\n *\n * 
$PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.35 
2007/01/05 22:19:25 momjian Exp $\n"...) at postgres.c:939
#14 0x1c18abb2 in PostgresMain (argc=1, argv=0xcf7df480, 
username=0x80ba55b0 "mastermind") at postgres.c:3423
#15 0x1c122102 in main (argc=10, argv=0xcf7df47c) at main.c:186


Stefan

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