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| author | Robert Haas <rhaas@postgresql.org> | 2016-03-18 09:46:40 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2016-03-18 09:50:05 -0400 |
| commit | 992b5ba30dcafdc222341505b072a6b009b248a7 (patch) | |
| tree | a05302f0aa1af5273f799221e18db5dbadaf8f7c /src/backend/utils/adt/misc.c | |
| parent | 2d8a1e22b109680204cb015a30e5a733a233ed64 (diff) | |
| download | postgresql-992b5ba30dcafdc222341505b072a6b009b248a7.tar.gz postgresql-992b5ba30dcafdc222341505b072a6b009b248a7.zip | |
Push scan/join target list beneath Gather when possible.
This means that, for example, "SELECT expensive_func(a) FROM bigtab
WHERE something" can compute expensive_func(a) in the workers rather
than the leader if it happens to be parallel-safe, which figures to be
a big win in some practical cases.
Currently, we can only do this if the entire target list is
parallel-safe. If we worked harder, we might be able to evaluate
parallel-safe targets in the worker and any parallel-restricted
targets in the leader, but that would be more complicated, and there
aren't that many parallel-restricted functions that people are likely
to use in queries anyway. I think. So just do the simple thing for
the moment.
Robert Haas, Amit Kapila, and Tom Lane
Diffstat (limited to 'src/backend/utils/adt/misc.c')
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