pgsql: Tom Lane <tgl@sss.pgh.pa.us> writes: > a_ogawa

Log Message:
-----------
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> a_ogawa <a_ogawa(at)hi-ho(dot)ne(dot)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 only
aset.c about this article.
I thought further: We can check whether context was used from the last
reset 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 : 33.7s

Atsushi Ogawa (a_ogawa)

Modified Files:
--------------
pgsql/src/backend/utils/mmgr:
aset.c (r1.60 -> r1.61)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mmgr/aset.c.diff?r1=1.60&r2=1.61)