On 02/03/2014 11:12 AM, Tom Lane wrote:
Andrew Dunstan <and...@dunslane.net> writes:
On 02/02/2014 08:54 PM, Craig Ringer wrote:
The attached patch deletes the context after use, bringing performance
back into line. It should be backpatched to 9.3.
Hmm. I guess I was assuming that the tmp_cxt would be cleaned up at the
end of the function since it's a child of the CurrentMemoryContext.
The executor does MemoryContextReset, not
MemoryContextResetAndDeleteChildren, on the per-tuple context.  That means
that child contexts will be reset, not deleted.  I seem to recall some
discussions about changing that, or even redefining MemoryContextReset to
automatically delete child contexts; but it would take a fair amount of
research to be sure such a change was safe.

Good to know.

Is it worth a note in src/backend/utils/mmgr/README so people are warned against making the same mistake I did? Both of these are set-returning functions operating in materialize mode - not sure if that makes any difference.



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