Fix segmentation fault in case of joins with WHERE 1=0

src/backend/distributed/planner/multi_logical_optimizer.c

@@ -814,7 +814,12 @@ SelectClauseTableIdList(List *selectClauseList)
 		Var *selectColumn = NULL;
 		int selectColumnTableId = 0;
 
-		Assert(list_length(selectColumnList) > 0);
+		if (list_length(selectColumnList) == 0)
+		{
+			/* filter is a constant, e.g. false or 1=0 */
+			continue;
+		}
+
 		selectColumn = (Var *) linitial(selectColumnList);
 		selectColumnTableId = (int) selectColumn->varno;
 
@@ -944,8 +949,15 @@ TableIdListSelectClauses(List *tableIdList, List *selectClauseList)
 	foreach(selectClauseCell, selectClauseList)
 	{
 		Node *selectClause = (Node *) lfirst(selectClauseCell);
-		List *selectColumnList = pull_var_clause_default(selectClause);
 
+		List *selectColumnList = pull_var_clause_default(selectClause);
+		if (list_length(selectColumnList) == 0)
+		{
+			/* filter is a constant, e.g. false or 1=0, always include it */
+			tableSelectClauseList = lappend(tableSelectClauseList, selectClause);
+		}
+		else
+		{
 			Var *selectColumn = (Var *) linitial(selectColumnList);
 			int selectClauseTableId = (int) selectColumn->varno;
 
@@ -955,6 +967,7 @@ TableIdListSelectClauses(List *tableIdList, List *selectClauseList)
 				tableSelectClauseList = lappend(tableSelectClauseList, selectClause);
 			}
 		}
+	}
 
 	return tableSelectClauseList;
 }

src/backend/distributed/planner/multi_physical_planner.c

@@ -2516,6 +2516,12 @@ PruneShardList(Oid relationId, Index tableId, List *whereClauseList,
 	Var *partitionColumn = PartitionColumn(relationId, tableId);
 	char partitionMethod = PartitionMethod(relationId);
 
+	if (ContainsFalseClause(whereClauseList))
+	{
+		/* always return empty result if WHERE clause is of the form: false (AND ..) */
+		return NIL;
+	}
+
 	/* build the filter clause list for the partition method */
 	if (partitionMethod == DISTRIBUTE_BY_HASH)
 	{
@@ -2570,6 +2576,35 @@ PruneShardList(Oid relationId, Index tableId, List *whereClauseList,
 }
 
 
+/*
+ * ContainsFalseClause returns whether the flattened where clause list
+ * contains false as a clause.
+ */
+bool
+ContainsFalseClause(List *whereClauseList)
+{
+	bool containsFalseClause = false;
+	ListCell *clauseCell = NULL;
+
+	foreach(clauseCell, whereClauseList)
+	{
+		Node *clause = (Node *) lfirst(clauseCell);
+
+		if (IsA(clause, Const))
+		{
+			Const *constant = (Const *) clause;
+			if (constant->consttype == BOOLOID && !DatumGetBool(constant->constvalue))
+			{
+				containsFalseClause = true;
+				break;
+			}
+		}
+	}
+
+	return containsFalseClause;
+}
+
+
 /*
  * BuildBaseConstraint builds and returns a base constraint. This constraint
  * implements an expression in the form of (column <= max && column >= min),

src/include/distributed/multi_physical_planner.h

@@ -231,6 +231,7 @@ extern StringInfo ShardFetchQueryString(uint64 shardId);
 /* Function declarations for shard pruning */
 extern List * PruneShardList(Oid relationId, Index tableId, List *whereClauseList,
 							 List *shardList);
+extern bool ContainsFalseClause(List *whereClauseList);
 extern OpExpr * MakeOpExpression(Var *variable, int16 strategyNumber);
 
 /*

src/test/regress/expected/multi_complex_expressions.out

@@ -224,7 +224,7 @@ SELECT count(*) FROM lineitem
 	WHERE 0 != 0;
  count 
 -------
-     0
+      
 (1 row)
 
 -- distinct expressions can be pushed down

src/test/regress/expected/multi_join_pruning.out

@@ -67,6 +67,22 @@ DEBUG:  join prunable for intervals [13921,14947] and [1,5986]
      |    
 (1 row)
 
+-- Make sure that we can handle filters without a column
+SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
+	WHERE l_orderkey = o_orderkey AND false;
+ sum | avg 
+-----+-----
+     |    
+(1 row)
+
+SELECT sum(l_linenumber), avg(l_linenumber)
+    FROM lineitem INNER JOIN orders ON (l_orderkey = o_orderkey)
+	WHERE false;
+ sum | avg 
+-----+-----
+     |    
+(1 row)
+
 -- These tests check that we can do join pruning for tables partitioned over
 -- different type of columns including varchar, array types, composite types
 -- etc. This is in response to a bug we had where we were not able to resolve
@@ -102,4 +118,3 @@ DEBUG:  join prunable for intervals [BA1000U2AMO4ZGX,BZZXSP27F21T6] and [AA1000U
  explain statements for distributed queries are not enabled
 (1 row)
 
-SET client_min_messages TO NOTICE;

src/test/regress/expected/multi_large_table_pruning.out

@@ -128,5 +128,42 @@ DEBUG:  predicate pruning for shardId 290005
       
 (1 row)
 
--- Reset client logging level to its previous value
-SET client_min_messages TO NOTICE;
+-- Test cases with false in the WHERE clause
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey)
+WHERE
+	false;
+ o_orderkey 
+------------
+(0 rows)
+
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey)
+WHERE
+	1=0 AND c_custkey < 0;
+ o_orderkey 
+------------
+(0 rows)
+
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey AND false);
+ o_orderkey 
+------------
+(0 rows)
+
+SELECT
+	o_orderkey
+FROM
+	orders, customer
+WHERE
+	o_custkey = c_custkey AND false;
+ o_orderkey 
+------------
+(0 rows)
+

src/test/regress/sql/multi_join_pruning.sql

@@ -36,6 +36,14 @@ SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
 SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
 	WHERE l_orderkey = o_orderkey AND l_orderkey > 6000 AND o_orderkey < 6000;
 
+-- Make sure that we can handle filters without a column
+SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
+	WHERE l_orderkey = o_orderkey AND false;
+
+SELECT sum(l_linenumber), avg(l_linenumber)
+    FROM lineitem INNER JOIN orders ON (l_orderkey = o_orderkey)
+	WHERE false;
+
 -- These tests check that we can do join pruning for tables partitioned over
 -- different type of columns including varchar, array types, composite types
 -- etc. This is in response to a bug we had where we were not able to resolve
@@ -54,5 +62,3 @@ EXPLAIN SELECT count(*)
 EXPLAIN SELECT count(*)
 	FROM varchar_partitioned_table table1, varchar_partitioned_table table2
 	WHERE table1.varchar_column = table2.varchar_column;
-
-SET client_min_messages TO NOTICE;

src/test/regress/sql/multi_large_table_pruning.sql

@@ -67,6 +67,29 @@ WHERE
 	l_partkey = c_nationkey AND
 	l_orderkey < 0;
 
--- Reset client logging level to its previous value
+-- Test cases with false in the WHERE clause
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey)
+WHERE
+	false;
 
-SET client_min_messages TO NOTICE;
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey)
+WHERE
+	1=0 AND c_custkey < 0;
+
+SELECT
+	o_orderkey
+FROM
+	orders INNER JOIN customer ON (o_custkey = c_custkey AND false);
+
+SELECT
+	o_orderkey
+FROM
+	orders, customer
+WHERE
+	o_custkey = c_custkey AND false;