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Support hashed aggregation with grouping sets.

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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
This commit is contained in:
Andrew Gierth
2017-03-27 04:20:54 +01:00
parent f0a6046bcb
commit b5635948ab
22 changed files with 2552 additions and 602 deletions
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4
src/include/optimizer/pathnode.h
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@@ -195,8 +195,8 @@ extern GroupingSetsPath *create_groupingsets_path(PlannerInfo *root,
Path *subpath,
PathTarget *target,
List *having_qual,
List *rollup_lists,
List *rollup_groupclauses,
AggStrategy aggstrategy,
List *rollups,
const AggClauseCosts *agg_costs,
double numGroups);
extern MinMaxAggPath *create_minmaxagg_path(PlannerInfo *root,