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Push tuple limits through Gather and Gather Merge.

author Robert Haas <rhaas@postgresql.org>

2017年8月29日 17:12:23 +0000 (13:12 -0400)

committer Robert Haas <rhaas@postgresql.org>

2017年8月29日 17:16:55 +0000 (13:16 -0400)

commit 3452dc5240da43e833118484e1e9b4894d04431c

tree d158d5d9630d80bc8a5ca838ba76eede60c77ba9 tree

parent ce5dcf54b942a469194ae390730f803b3f3fb928 commit | diff

Push tuple limits through Gather and Gather Merge.

If we only need, say, 10 tuples in total, then we certainly don't need
more than 10 tuples from any single process. Pushing down the limit
lets workers exit early when possible. For Gather Merge, there is
an additional benefit: a Sort immediately below the Gather Merge can
be done as a bounded sort if there is an applicable limit.

Robert Haas and Tom Lane

Discussion: http://postgr.es/m/CA+TgmoYa3QKKrLj5rX7UvGqhH73G1Li4B-EKxrmASaca2tFu9Q@mail.gmail.com

src/backend/executor/execParallel.c diff | blob | blame | history

src/backend/executor/execProcnode.c diff | blob | blame | history

src/backend/executor/nodeGather.c diff | blob | blame | history

src/backend/executor/nodeGatherMerge.c diff | blob | blame | history

src/backend/executor/nodeLimit.c diff | blob | blame | history

src/include/executor/execParallel.h diff | blob | blame | history

src/include/executor/executor.h diff | blob | blame | history

src/include/nodes/execnodes.h diff | blob | blame | history

src/test/regress/expected/select_parallel.out diff | blob | blame | history

src/test/regress/sql/select_parallel.sql diff | blob | blame | history

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