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Commit3cf1fd3

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Tom Lane <tgl@sss.pgh.pa.us> writes:
> a_ogawa <a_ogawa@hi-ho.ne.jp> writes:> > It is a reasonable idea. However, the majority part of MemSet was not> > able to be avoided by this idea. Because the per-tuple contexts are used> > at the early stage of executor.>> Drat. Well, what about changing that? We could introduce additional> contexts or change the startup behavior so that the ones that are> frequently reset don't have any data in them unless you are working> with pass-by-ref values inside the inner loop.That might be possible. However, I think that we should change onlyaset.c about this article.I thought further: We can check whether context was used from the lastreset even when blocks list is not empty. Please see attached patch.The effect of the patch that I measured is as follows:o Execution time that executed the SQL ten times.(1)Linux(CPU: Pentium III, Compiler option: -O2) - original: 24.960s - patched : 23.114s(2)Linux(CPU: Pentium 4, Compiler option: -O2) - original: 8.730s - patched : 7.962s(3)Solaris(CPU: Ultra SPARC III, Compiler option: -O2) - original: 37.0s - patched : 33.7sAtsushi Ogawa (a_ogawa)
1 parente18e8f8 commit3cf1fd3

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‎src/backend/utils/mmgr/aset.c‎

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.60 2005/05/14 20:29:13 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.61 2005/06/04 20:14:12 momjian Exp $
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*
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* NOTE:
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*This is a new (Feb. 05, 1999) implementation of the allocation set
@@ -399,6 +399,17 @@ AllocSetReset(MemoryContext context)
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if (block==NULL)
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return;
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/*
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* When blocks list has only "keeper" block and freeptr of the block
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* is initial value, the context is not used from last reset.
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*/
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if (block==set->keeper&&block->next==NULL)
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{
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char*datastart= ((char*)block)+ALLOC_BLOCKHDRSZ;
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if (block->freeptr==datastart)
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return;
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}
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/* Clear chunk freelists */
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MemSetAligned(set->freelist,0,sizeof(set->freelist));
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