Disallow creation of indexes on system columns (except for OID).

Although OID acts pretty much like user data, the other system columns do
not, so an index on one would likely misbehave.  And it's pretty hard to
see a use-case for one, anyway.  Let's just forbid the case rather than
worry about whether it should be supported.

David Rowley

1 files changed, 37 insertions, 0 deletions

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 13b04e68f01..d14d540b26e 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -18,6 +18,7 @@
 #include "access/amapi.h"
 #include "access/htup_details.h"
 #include "access/reloptions.h"
+#include "access/sysattr.h"
 #include "access/xact.h"
 #include "catalog/catalog.h"
 #include "catalog/index.h"
@@ -37,6 +38,7 @@
 #include "nodes/nodeFuncs.h"
 #include "optimizer/clauses.h"
 #include "optimizer/planner.h"
+#include "optimizer/var.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
 #include "parser/parse_oper.h"
@@ -575,6 +577,41 @@ DefineIndex(Oid relationId,
 		index_check_primary_key(rel, indexInfo, is_alter_table);
 
 	/*
+	 * We disallow indexes on system columns other than OID.  They would not
+	 * necessarily get updated correctly, and they don't seem useful anyway.
+	 */
+	for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
+	{
+		AttrNumber	attno = indexInfo->ii_KeyAttrNumbers[i];
+
+		if (attno < 0 && attno != ObjectIdAttributeNumber)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			   errmsg("index creation on system columns is not supported")));
+	}
+
+	/*
+	 * Also check for system columns used in expressions or predicates.
+	 */
+	if (indexInfo->ii_Expressions || indexInfo->ii_Predicate)
+	{
+		Bitmapset  *indexattrs = NULL;
+
+		pull_varattnos((Node *) indexInfo->ii_Expressions, 1, &indexattrs);
+		pull_varattnos((Node *) indexInfo->ii_Predicate, 1, &indexattrs);
+
+		for (i = FirstLowInvalidHeapAttributeNumber + 1; i < 0; i++)
+		{
+			if (i != ObjectIdAttributeNumber &&
+				bms_is_member(i - FirstLowInvalidHeapAttributeNumber,
+							  indexattrs))
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				errmsg("index creation on system columns is not supported")));
+		}
+	}
+
+	/*
 	 * Report index creation if appropriate (delay this till after most of the
 	 * error checks)
 	 */