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Improve planner's choices about when to use hashing vs sorting for DISTINCT.

author Tom Lane <tgl@sss.pgh.pa.us>

2010年2月10日 03:38:35 +0000 (03:38 +0000)

committer Tom Lane <tgl@sss.pgh.pa.us>

2010年2月10日 03:38:35 +0000 (03:38 +0000)

commit 76b6ee3f380b90956a1ca18f15e2a70874651f66

tree 6c2bbc7bfab237f7cf51b006f7698d2abf4a9085 tree

parent cbe9d6beb4ae1cb20c08cab29b534be4923b6768 commit | diff

Improve planner's choices about when to use hashing vs sorting for DISTINCT.

The previous coding missed a bet by sometimes picking the "sorted" path
from query_planner even though hashing would be preferable. To fix, we have
to be willing to make the choice sooner. This contorts things a little bit,
but I thought of a factorization that makes it not too awful.

src/backend/optimizer/plan/planner.c diff | blob | blame | history

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