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| author | Andrew Gierth <rhodiumtoad@postgresql.org> | 2017-03-27 04:20:54 +0100 |
|---|---|---|
| committer | Andrew Gierth <rhodiumtoad@postgresql.org> | 2017-03-27 04:20:54 +0100 |
| commit | b5635948ab165b6070e7d05d111f966e07570d81 (patch) | |
| tree | 9e8581fa3530ea777b14ce4900ba7cea106e3450 /src/backend/utils/adt/ruleutils.c | |
| parent | f0a6046bcb15c2fe48384ef547df2bfb5d7f0a89 (diff) | |
| download | postgresql-b5635948ab165b6070e7d05d111f966e07570d81.tar.gz postgresql-b5635948ab165b6070e7d05d111f966e07570d81.zip | |
Support hashed aggregation with grouping sets.
This extends the Aggregate node with two new features: HashAggregate
can now run multiple hashtables concurrently, and a new strategy
MixedAggregate populates hashtables while doing sorted grouping.
The planner will now attempt to save as many sorts as possible when
planning grouping sets queries, while not exceeding work_mem for the
estimated combined sizes of all hashtables used. No SQL-level changes
are required. There should be no user-visible impact other than the
new EXPLAIN output and possible changes to result ordering when ORDER
BY was not used (which affected a few regression tests). The
enable_hashagg option is respected.
Author: Andrew Gierth
Reviewers: Mark Dilger, Andres Freund
Discussion: https://postgr.es/m/87vatszyhj.fsf@news-spur.riddles.org.uk
Diffstat (limited to 'src/backend/utils/adt/ruleutils.c')
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