pgsql: Back out patch:

Log Message:
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Back out patch:

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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.

Modified Files:
--------------
pgsql/src/backend/utils/mmgr:
aset.c (r1.61 -> r1.62)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mmgr/aset.c.diff?r1=1.61&r2=1.62)