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

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.

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 893bb006b3dd91e1eb8ce7922307eeeb65880d36..737b093a1b4b99e7ab5cfe13bf7e9d4de6d1548d 100644 (file)
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1025,6 +1025,16 @@ 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;

diff --git a/src/include/access/attnum.h b/src/include/access/attnum.h
index 3050348ed386fb1e6e769629eac75ff9ab4aec04..e479e5479a64b694224d45d114c95c20dc8036f8 100644 (file)
--- a/src/include/access/attnum.h
+++ b/src/include/access/attnum.h
@@ -21,6 +21,7 @@
 typedef int16 AttrNumber;
 
 #define InvalidAttrNumber              0
+#define MaxAttrNumber                  32767
 
 /* ----------------
  *             support macros