Avoid an Assert failure in deconstruct_array() by making get_attstatsslot()

tglsfdc · tglsfdc · commit dae11908e8df · 2010-07-09T22:58:12.000Z
use the actual element type of the array it's disassembling, rather than
trusting the type OID passed in by its caller.  This is needed because
sometimes the planner passes in a type OID that's only binary-compatible
with the target column's type, rather than being an exact match.  Per an
example from Bernd Helmle.

Possibly we should refactor get_attstatsslot/free_attstatsslot to not expect
the caller to supply type ID data at all, but for now I'll just do the
minimum-change fix.

Back-patch to 7.4.  Bernd's test case only crashes back to 8.0, but since
these subroutines are the same in 7.4, I suspect there may be variant
cases that would crash 7.4 as well.
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.129.2.1 2007/10/13 15:55:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.129.2.2 2010/07/09 22:58:12 tgl Exp $
  *
  * NOTES
  *	  Eventually, the index information should go through here, too.
@@ -1881,6 +1881,10 @@ get_attavgwidth(Oid relid, AttrNumber attnum)
  * If the attribute type is pass-by-reference, the values referenced by
  * the values array are themselves palloc'd.  The palloc'd stuff can be
  * freed by calling free_attstatsslot.
+ *
+ * Note: at present, atttype/atttypmod aren't actually used here at all.
+ * But the caller must have the correct (or at least binary-compatible)
+ * type ID to pass to free_attstatsslot later.
  */
 bool
 get_attstatsslot(HeapTuple statstuple,
@@ -1895,6 +1899,7 @@ get_attstatsslot(HeapTuple statstuple,
 	Datum		val;
 	bool		isnull;
 	ArrayType  *statarray;
+	Oid			arrayelemtype;
 	int			narrayelem;
 	HeapTuple	typeTuple;
 	Form_pg_type typeForm;
@@ -1917,17 +1922,24 @@ get_attstatsslot(HeapTuple statstuple,
 			elog(ERROR, "stavalues is null");
 		statarray = DatumGetArrayTypeP(val);
 
-		/* Need to get info about the array element type */
+		/*
+		 * Need to get info about the array element type.  We look at the
+		 * actual element type embedded in the array, which might be only
+		 * binary-compatible with the passed-in atttype.  The info we
+		 * extract here should be the same either way, but deconstruct_array
+		 * is picky about having an exact type OID match.
+		 */
+		arrayelemtype = ARR_ELEMTYPE(statarray);
 		typeTuple = SearchSysCache(TYPEOID,
-								   ObjectIdGetDatum(atttype),
+								   ObjectIdGetDatum(arrayelemtype),
 								   0, 0, 0);
 		if (!HeapTupleIsValid(typeTuple))
-			elog(ERROR, "cache lookup failed for type %u", atttype);
+			elog(ERROR, "cache lookup failed for type %u", arrayelemtype);
 		typeForm = (Form_pg_type) GETSTRUCT(typeTuple);
 
 		/* Deconstruct array into Datum elements */
 		deconstruct_array(statarray,
-						  atttype,
+						  arrayelemtype,
 						  typeForm->typlen,
 						  typeForm->typbyval,
 						  typeForm->typalign,
