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Defend against JOINs having more than 32K columns altogether. We cannot

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currently support this because we must be able to build Vars referencing
join columns, and varattno is only 16 bits wide.  Perhaps this should be
improved in future, but considering that it never came up before, I'm not
sure the problem is worth much effort.  Per bug #4070 from Marcello
Ceschia.

The problem seems largely academic in 8.0 and 7.4, because they have
(different) O(N^2) performance issues with such wide joins, but
back-patch all the way anyway.
This commit is contained in:
Tom Lane 2008-04-05 01:58:42 +00:00
parent 80dc9a8e19
commit 19d262540c
2 changed files with 13 additions and 2 deletions
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12
src/backend/parser/parse_relation.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.116.2.2 2006/01/10 22:00:07 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.116.2.3 2008/04/05 01:58:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -935,6 +935,16 @@ addRangeTableEntryForJoin(ParseState *pstate,
Alias *eref;
int numaliases;
/*
* Fail if join has too many columns --- we must be able to reference
* any of the columns with an AttrNumber.
*/
if (list_length(aliasvars) > MaxAttrNumber)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("joins can have at most %d columns",
MaxAttrNumber)));
rte->rtekind = RTE_JOIN;
rte->relid = InvalidOid;
rte->subquery = NULL;

3
src/include/access/attnum.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.21 2005/05/25 21:40:42 momjian Exp $
* $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.21.2.1 2008/04/05 01:58:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -21,6 +21,7 @@
typedef int16 AttrNumber;
#define InvalidAttrNumber 0
#define MaxAttrNumber 32767
/* ----------------
* support macros