database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-28 11:44:57 +03:00
Code Activity

Adjust hash table sizing algorithm to avoid integer overflow in

Browse Source 
ExecHashJoinGetBatch().  Fixes core dump on large hash joins, as in
example from Rae Stiening.
This commit is contained in:
Tom Lane
2002-12-29 22:29:03 +00:00
parent b37d6373f0
commit 629df5f489
1 changed files with 23 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
src/backend/executor/nodeHash.c
View File

@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* $Id: nodeHash.c,v 1.66 2002/09/04 20:31:18 momjian Exp $
* $Id: nodeHash.c,v 1.66.2.1 2002/12/29 22:29:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -19,6 +19,7 @@
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/hash.h"
@@ -342,7 +343,8 @@ ExecChooseHashTableSize(double ntuples, int tupwidth,
{
int tupsize;
double inner_rel_bytes;
double hash_table_bytes;
long hash_table_bytes;
double dtmp;
int nbatch;
int nbuckets;
int totalbuckets;
@@ -360,20 +362,22 @@ ExecChooseHashTableSize(double ntuples, int tupwidth,
inner_rel_bytes = ntuples * tupsize * FUDGE_FAC;
/*
* Target hashtable size is SortMem kilobytes, but not less than
* sqrt(estimated inner rel size), so as to avoid horrible
* performance.
* Target in-memory hashtable size is SortMem kilobytes.
*/
hash_table_bytes = sqrt(inner_rel_bytes);
if (hash_table_bytes < (SortMem * 1024L))
hash_table_bytes = SortMem * 1024L;
hash_table_bytes = SortMem * 1024L;
/*
* Count the number of hash buckets we want for the whole relation,
* for an average bucket load of NTUP_PER_BUCKET (per virtual
* bucket!).
* bucket!). It has to fit in an int, however.
*/
totalbuckets = (int) ceil(ntuples * FUDGE_FAC / NTUP_PER_BUCKET);
dtmp = ceil(ntuples * FUDGE_FAC / NTUP_PER_BUCKET);
if (dtmp < INT_MAX)
totalbuckets = (int) dtmp;
else
totalbuckets = INT_MAX;
if (totalbuckets <= 0)
totalbuckets = 1;
/*
* Count the number of buckets we think will actually fit in the
@@ -407,10 +411,16 @@ ExecChooseHashTableSize(double ntuples, int tupwidth,
* that nbatch doesn't have to have anything to do with the ratio
* totalbuckets/nbuckets; in fact, it is the number of groups we
* will use for the part of the data that doesn't fall into the
* first nbuckets hash buckets.
* first nbuckets hash buckets. We try to set it to make all the
* batches the same size. But we have to keep nbatch small
* enough to avoid integer overflow in ExecHashJoinGetBatch().
*/
nbatch = (int) ceil((inner_rel_bytes - hash_table_bytes) /
hash_table_bytes);
dtmp = ceil((inner_rel_bytes - hash_table_bytes) /
hash_table_bytes);
if (dtmp < INT_MAX / totalbuckets)
nbatch = (int) dtmp;
else
nbatch = INT_MAX / totalbuckets;
if (nbatch <= 0)
nbatch = 1;
}