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Adjust hash table sizing algorithm to avoid integer overflow in

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ExecHashJoinGetBatch().  Fixes core dump on large hash joins, as in
example from Rae Stiening.
This commit is contained in:
Tom Lane 2002-12-29 22:28:50 +00:00
parent c9d8712043
commit b33265e9e6
1 changed files with 23 additions and 13 deletions

36
src/backend/executor/nodeHash.c

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.71 2002/12/15 16:17:46 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/nodeHash.c,v 1.72 2002/12/29 22:28:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -20,6 +20,7 @@
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/hash.h"
@ -344,7 +345,8 @@ 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;
@ -362,20 +364,22 @@ 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
@ -409,10 +413,16 @@ 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;
}