Fix core dump in QTNodeCompare when tsquery_cmp() is applied to two empty

tsqueries.  CompareTSQ has to have a guard for the case rather than blindly
applying QTNodeCompare to random data past the end of the datums.  Also,
change QTNodeCompare to be a little less trusting: use an actual test rather
than just Assert'ing that the input is sane.  Problem encountered while
investigating another issue (I saw a core dump in autoanalyze on a table
containing multiple empty tsquery values).

Back-patch to all branches with tsquery support.

In HEAD, also fix some bizarre (though not outright wrong) coding in
tsq_mcontains().

src/backend/utils/adt/tsquery_op.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_op.c,v 1.8 2010/01/02 16:57:55 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_op.c,v 1.9 2010/08/03 00:10:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -149,7 +149,7 @@ CompareTSQ(TSQuery a, TSQuery b)
 	{
 		return (VARSIZE(a) < VARSIZE(b)) ? -1 : 1;
 	}
-	else
+	else if (a->size != 0)
 	{
 		QTNode	   *an = QT2QTN(GETQUERY(a), GETOPERAND(a));
 		QTNode	   *bn = QT2QTN(GETQUERY(b), GETOPERAND(b));
@@ -247,20 +247,20 @@ tsq_mcontains(PG_FUNCTION_ARGS)
 		PG_RETURN_BOOL(false);
 	}
 
+	iq = GETQUERY(query);
 	ie = GETQUERY(ex);
 
 	for (i = 0; i < ex->size; i++)
 	{
-		iq = GETQUERY(query);
 		if (ie[i].type != QI_VAL)
 			continue;
 		for (j = 0; j < query->size; j++)
-			if (iq[j].type == QI_VAL && ie[i].qoperand.valcrc == iq[j].qoperand.valcrc)
-			{
-				j = query->size + 1;
+		{
+			if (iq[j].type == QI_VAL &&
+				ie[i].qoperand.valcrc == iq[j].qoperand.valcrc)
 				break;
-			}
-		if (j == query->size)
+		}
+		if (j >= query->size)
 		{
 			PG_FREE_IF_COPY(query, 0);
 			PG_FREE_IF_COPY(ex, 1);

src/backend/utils/adt/tsquery_util.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_util.c,v 1.13 2010/01/02 16:57:55 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_util.c,v 1.14 2010/08/03 00:10:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -113,13 +113,11 @@ QTNodeCompare(QTNode *an, QTNode *bn)
 		}
 		return 0;
 	}
-	else
+	else if (an->valnode->type == QI_VAL)
 	{
 		QueryOperand *ao = &an->valnode->qoperand;
 		QueryOperand *bo = &bn->valnode->qoperand;
 
-		Assert(an->valnode->type == QI_VAL);
-
 		if (ao->valcrc != bo->valcrc)
 		{
 			return (ao->valcrc > bo->valcrc) ? -1 : 1;
@@ -127,6 +125,11 @@ QTNodeCompare(QTNode *an, QTNode *bn)
 
 		return tsCompareString(an->word, ao->length, bn->word, bo->length, false);
 	}
+	else
+	{
+		elog(ERROR, "unrecognized QueryItem type: %d", an->valnode->type);
+		return 0;				/* keep compiler quiet */
+	}
 }
 
 static int