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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2002-11-19 23:22:00 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2002-11-19 23:22:00 +0000 |
| commit | b60be3f2f8d094da79e04c6eda888f401b09dc39 (patch) | |
| tree | 0590e0647deb5041b8dabcabf03770ebef8e8d43 /src/backend/executor/nodeAgg.c | |
| parent | 54cb1db6cf4d4bf4e44148582bbd2c99684e7dfd (diff) | |
| download | postgresql-b60be3f2f8d094da79e04c6eda888f401b09dc39.tar.gz postgresql-b60be3f2f8d094da79e04c6eda888f401b09dc39.zip | |
Add an at-least-marginally-plausible method of estimating the number
of groups produced by GROUP BY. This improves the accuracy of planning
estimates for grouped subselects, and is needed to check whether a
hashed aggregation plan risks memory overflow.
Diffstat (limited to 'src/backend/executor/nodeAgg.c')
| -rw-r--r-- | src/backend/executor/nodeAgg.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c index 5fa82ee9fad..0216f8ebde7 100644 --- a/src/backend/executor/nodeAgg.c +++ b/src/backend/executor/nodeAgg.c @@ -45,7 +45,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.95 2002/11/13 00:39:47 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.96 2002/11/19 23:21:57 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -619,6 +619,9 @@ lookup_hash_entry(Agg *node, TupleTableSlot *slot) Datum attr; bool isNull; + /* rotate hashkey left 1 bit at each step */ + hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0); + attr = heap_getattr(tuple, att, tupdesc, &isNull); if (isNull) continue; /* treat nulls as having hash key 0 */ |