database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-30 21:42:05 +03:00
Code Activity

Add an at-least-marginally-plausible method of estimating the number

Browse Source 
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.
This commit is contained in:
Tom Lane
2002-11-19 23:22:00 +00:00
parent 54cb1db6cf
commit b60be3f2f8
11 changed files with 454 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
src/backend/executor/nodeAgg.c
View File

@ -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 */