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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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30
src/backend/nodes/bitmapset.c
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@ -21,6 +21,7 @@
#include "postgres.h"
#include "access/hash.h"
#include "nodes/pg_list.h"
#define WORDNUM(x) ((x) / BITS_PER_BITMAPWORD)
@ -457,6 +458,35 @@ bms_overlap(const Bitmapset *a, const Bitmapset *b)
return false;
}
/*
* bms_overlap_list - does a set overlap an integer list?
*/
bool
bms_overlap_list(const Bitmapset *a, const List *b)
{
ListCell *lc;
int wordnum,
bitnum;
if (a == NULL || b == NIL)
return false;
foreach(lc, b)
{
int x = lfirst_int(lc);
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
if (wordnum < a->nwords)
if ((a->words[wordnum] & ((bitmapword) 1 << bitnum)) != 0)
return true;
}
return false;
}
/*
* bms_nonempty_difference - do sets have a nonempty difference?
*/