Allow cartesian products on reference tables

src/backend/distributed/planner/multi_join_order.c

@@ -76,6 +76,10 @@ static RuleEvalFunction JoinRuleEvalFunction(JoinRuleType ruleType);
 static char * JoinRuleName(JoinRuleType ruleType);
 static JoinOrderNode * ReferenceJoin(JoinOrderNode *joinNode, TableEntry *candidateTable,
 									 List *applicableJoinClauses, JoinType joinType);
+static JoinOrderNode * CartesianProductReferenceJoin(JoinOrderNode *joinNode,
+													 TableEntry *candidateTable,
+													 List *applicableJoinClauses,
+													 JoinType joinType);
 static JoinOrderNode * LocalJoin(JoinOrderNode *joinNode, TableEntry *candidateTable,
 								 List *applicableJoinClauses, JoinType joinType);
 static bool JoinOnColumns(Var *currentPartitioncolumn, Var *candidatePartitionColumn,
@@ -752,6 +756,8 @@ JoinRuleEvalFunction(JoinRuleType ruleType)
 		RuleEvalFunctionArray[SINGLE_RANGE_PARTITION_JOIN] = &SinglePartitionJoin;
 		RuleEvalFunctionArray[SINGLE_HASH_PARTITION_JOIN] = &SinglePartitionJoin;
 		RuleEvalFunctionArray[DUAL_PARTITION_JOIN] = &DualPartitionJoin;
+		RuleEvalFunctionArray[CARTESIAN_PRODUCT_REFERENCE_JOIN] =
+			&CartesianProductReferenceJoin;
 		RuleEvalFunctionArray[CARTESIAN_PRODUCT] = &CartesianProduct;
 
 		ruleEvalFunctionsInitialized = true;
@@ -780,6 +786,8 @@ JoinRuleName(JoinRuleType ruleType)
 		RuleNameArray[SINGLE_RANGE_PARTITION_JOIN] =
 			strdup("single range partition join");
 		RuleNameArray[DUAL_PARTITION_JOIN] = strdup("dual partition join");
+		RuleNameArray[CARTESIAN_PRODUCT_REFERENCE_JOIN] = strdup(
+			"cartesian product reference join");
 		RuleNameArray[CARTESIAN_PRODUCT] = strdup("cartesian product");
 
 		ruleNamesInitialized = true;
@@ -801,48 +809,76 @@ static JoinOrderNode *
 ReferenceJoin(JoinOrderNode *currentJoinNode, TableEntry *candidateTable,
 			  List *applicableJoinClauses, JoinType joinType)
 {
-	JoinOrderNode *nextJoinNode = NULL;
 	int applicableJoinCount = list_length(applicableJoinClauses);
-	char candidatePartitionMethod = PartitionMethod(candidateTable->relationId);
-	char leftPartitionMethod = PartitionMethod(currentJoinNode->tableEntry->relationId);
-	bool performReferenceJoin = false;
-
 	if (applicableJoinCount <= 0)
 	{
 		return NULL;
 	}
 
-	/*
-	 * If the table is a reference table, then the reference join is feasible.It
-	 * is valid only for inner joins.
-	 *
-	 * Right join requires existing (left) table to be reference table, full outer
-	 * join requires both tables to be reference tables.
-	 */
-	if ((joinType == JOIN_INNER || joinType == JOIN_LEFT || joinType == JOIN_ANTI) &&
-		candidatePartitionMethod == DISTRIBUTE_BY_NONE)
-	{
-		performReferenceJoin = true;
-	}
-	else if (joinType == JOIN_RIGHT && leftPartitionMethod == DISTRIBUTE_BY_NONE)
-	{
-		performReferenceJoin = true;
-	}
-	else if (joinType == JOIN_FULL && leftPartitionMethod == DISTRIBUTE_BY_NONE &&
-			 candidatePartitionMethod == DISTRIBUTE_BY_NONE)
-	{
-		performReferenceJoin = true;
-	}
+	char candidatePartitionMethod = PartitionMethod(candidateTable->relationId);
+	char leftPartitionMethod = PartitionMethod(currentJoinNode->tableEntry->relationId);
 
-	if (performReferenceJoin)
+	if (!IsSupportedReferenceJoin(joinType,
+								  leftPartitionMethod == DISTRIBUTE_BY_NONE,
+								  candidatePartitionMethod == DISTRIBUTE_BY_NONE))
 	{
-		nextJoinNode = MakeJoinOrderNode(candidateTable, REFERENCE_JOIN,
+		return NULL;
+	}
+	return MakeJoinOrderNode(candidateTable, REFERENCE_JOIN,
 							 currentJoinNode->partitionColumn,
 							 currentJoinNode->partitionMethod,
 							 currentJoinNode->anchorTable);
-	}
+}
 
-	return nextJoinNode;
+
+/*
+ * IsSupportedReferenceJoin checks if with this join type we can safely do a simple join
+ * on the reference table on all the workers.
+ */
+bool
+IsSupportedReferenceJoin(JoinType joinType, bool leftIsReferenceTable,
+						 bool rightIsReferenceTable)
+{
+	if ((joinType == JOIN_INNER || joinType == JOIN_LEFT || joinType == JOIN_ANTI) &&
+		rightIsReferenceTable)
+	{
+		return true;
+	}
+	else if ((joinType == JOIN_RIGHT) &&
+			 leftIsReferenceTable)
+	{
+		return true;
+	}
+	else if (joinType == JOIN_FULL && leftIsReferenceTable && rightIsReferenceTable)
+	{
+		return true;
+	}
+	return false;
+}
+
+
+/*
+ * ReferenceJoin evaluates if the candidate table is a reference table for inner,
+ * left and anti join. For right join, current join node must be represented by
+ * a reference table. For full join, both of them must be a reference table.
+ */
+static JoinOrderNode *
+CartesianProductReferenceJoin(JoinOrderNode *currentJoinNode, TableEntry *candidateTable,
+							  List *applicableJoinClauses, JoinType joinType)
+{
+	char candidatePartitionMethod = PartitionMethod(candidateTable->relationId);
+	char leftPartitionMethod = PartitionMethod(currentJoinNode->tableEntry->relationId);
+
+	if (!IsSupportedReferenceJoin(joinType,
+								  leftPartitionMethod == DISTRIBUTE_BY_NONE,
+								  candidatePartitionMethod == DISTRIBUTE_BY_NONE))
+	{
+		return NULL;
+	}
+	return MakeJoinOrderNode(candidateTable, CARTESIAN_PRODUCT_REFERENCE_JOIN,
+							 currentJoinNode->partitionColumn,
+							 currentJoinNode->partitionMethod,
+							 currentJoinNode->anchorTable);
 }
 
 

src/backend/distributed/planner/multi_logical_planner.c

@@ -115,6 +115,11 @@ static MultiJoin * ApplySinglePartitionJoin(MultiNode *leftNode, MultiNode *righ
 static MultiNode * ApplyDualPartitionJoin(MultiNode *leftNode, MultiNode *rightNode,
 										  Var *partitionColumn, JoinType joinType,
 										  List *joinClauses);
+static MultiNode * ApplyCartesianProductReferenceJoin(MultiNode *leftNode,
+													  MultiNode *rightNode,
+													  Var *partitionColumn,
+													  JoinType joinType,
+													  List *joinClauses);
 static MultiNode * ApplyCartesianProduct(MultiNode *leftNode, MultiNode *rightNode,
 										 Var *partitionColumn, JoinType joinType,
 										 List *joinClauses);
@@ -2022,6 +2027,8 @@ JoinRuleApplyFunction(JoinRuleType ruleType)
 		RuleApplyFunctionArray[SINGLE_RANGE_PARTITION_JOIN] =
 			&ApplySingleRangePartitionJoin;
 		RuleApplyFunctionArray[DUAL_PARTITION_JOIN] = &ApplyDualPartitionJoin;
+		RuleApplyFunctionArray[CARTESIAN_PRODUCT_REFERENCE_JOIN] =
+			&ApplyCartesianProductReferenceJoin;
 		RuleApplyFunctionArray[CARTESIAN_PRODUCT] = &ApplyCartesianProduct;
 
 		ruleApplyFunctionInitialized = true;
@@ -2055,6 +2062,28 @@ ApplyReferenceJoin(MultiNode *leftNode, MultiNode *rightNode,
 }
 
 
+/*
+ * ApplyCartesianProductReferenceJoin creates a new MultiJoin node that joins
+ * the left and the right node. The new node uses the broadcast join rule to
+ * perform the join.
+ */
+static MultiNode *
+ApplyCartesianProductReferenceJoin(MultiNode *leftNode, MultiNode *rightNode,
+								   Var *partitionColumn, JoinType joinType,
+								   List *applicableJoinClauses)
+{
+	MultiJoin *joinNode = CitusMakeNode(MultiJoin);
+	joinNode->joinRuleType = CARTESIAN_PRODUCT_REFERENCE_JOIN;
+	joinNode->joinType = joinType;
+	joinNode->joinClauseList = applicableJoinClauses;
+
+	SetLeftChild((MultiBinaryNode *) joinNode, leftNode);
+	SetRightChild((MultiBinaryNode *) joinNode, rightNode);
+
+	return (MultiNode *) joinNode;
+}
+
+
 /*
  * ApplyLocalJoin creates a new MultiJoin node that joins the left and the right
  * node. The new node uses the local join rule to perform the join.

src/backend/distributed/planner/multi_physical_planner.c

@@ -3457,6 +3457,28 @@ FragmentCombinationList(List *rangeTableFragmentsList, Query *jobQuery,
 }
 
 
+/*
+ * NodeIsRangeTblRefReferenceTable checks if the node is a RangeTblRef that
+ * points to a reference table in the rangeTableList.
+ */
+static bool
+NodeIsRangeTblRefReferenceTable(Node *node, List *rangeTableList)
+{
+	if (!IsA(node, RangeTblRef))
+	{
+		return false;
+	}
+	RangeTblRef *tableRef = castNode(RangeTblRef, node);
+	RangeTblEntry *rangeTableEntry = rt_fetch(tableRef->rtindex, rangeTableList);
+	CitusRTEKind rangeTableType = GetRangeTblKind(rangeTableEntry);
+	if (rangeTableType != CITUS_RTE_RELATION)
+	{
+		return false;
+	}
+	return PartitionMethod(rangeTableEntry->relid) == DISTRIBUTE_BY_NONE;
+}
+
+
 /*
  * JoinSequenceArray walks over the join nodes in the job query and constructs a join
  * sequence containing an entry for each joined table. The function then returns an
@@ -3496,18 +3518,26 @@ JoinSequenceArray(List *rangeTableFragmentsList, Query *jobQuery, List *dependen
 	foreach(joinExprCell, joinExprList)
 	{
 		JoinExpr *joinExpr = (JoinExpr *) lfirst(joinExprCell);
-		RangeTblRef *rightTableRef = (RangeTblRef *) joinExpr->rarg;
+		RangeTblRef *rightTableRef = castNode(RangeTblRef, joinExpr->rarg);
 		uint32 nextRangeTableId = rightTableRef->rtindex;
 		Index existingRangeTableId = 0;
 		bool applyJoinPruning = false;
 
 		List *nextJoinClauseList = make_ands_implicit((Expr *) joinExpr->quals);
+		bool leftIsReferenceTable = NodeIsRangeTblRefReferenceTable(joinExpr->larg,
+																	rangeTableList);
+		bool rightIsReferenceTable = NodeIsRangeTblRefReferenceTable(joinExpr->rarg,
+																	 rangeTableList);
+		bool isReferenceJoin = IsSupportedReferenceJoin(joinExpr->jointype,
+														leftIsReferenceTable,
+														rightIsReferenceTable);
 
 		/*
 		 * If next join clause list is empty, the user tried a cartesian product
-		 * between tables. We don't support this functionality, and error out.
+		 * between tables. We don't support this functionality for non
+		 * reference joins, and error out.
 		 */
-		if (nextJoinClauseList == NIL)
+		if (nextJoinClauseList == NIL && !isReferenceJoin)
 		{
 			ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							errmsg("cannot perform distributed planning on this query"),

src/include/distributed/multi_join_order.h

@@ -35,7 +35,8 @@ typedef enum JoinRuleType
 	SINGLE_HASH_PARTITION_JOIN = 3,
 	SINGLE_RANGE_PARTITION_JOIN = 4,
 	DUAL_PARTITION_JOIN = 5,
-	CARTESIAN_PRODUCT = 6,
+	CARTESIAN_PRODUCT_REFERENCE_JOIN = 6,
+	CARTESIAN_PRODUCT = 7,
 
 	/*
 	 * Add new join rule types above this comment. After adding, you must also
@@ -89,6 +90,8 @@ extern bool IsApplicableJoinClause(List *leftTableIdList, uint32 rightTableId,
 extern List * ApplicableJoinClauses(List *leftTableIdList, uint32 rightTableId,
 									List *joinClauseList);
 extern bool NodeIsEqualsOpExpr(Node *node);
+extern bool IsSupportedReferenceJoin(JoinType joinType, bool leftIsReferenceTable,
+									 bool rightIsReferenceTable);
 extern OpExpr * SinglePartitionJoinClause(Var *partitionColumn,
 										  List *applicableJoinClauses);
 extern OpExpr * DualPartitionJoinClause(List *applicableJoinClauses);

src/test/regress/expected/expression_reference_join.out

@@ -41,8 +41,11 @@ ORDER BY 1,2,3;
  2 | 2 | 2 | 4 | 4
 (4 rows)
 
--- The join clause is wider than it used to be, causing this query to be recognized by the LogicalPlanner as a repartition join.
--- Unplannable query due to a three-way join which causes no valid path (besides the cartesian product) to be found
+-- The join clause is wider than it used to be, causing this query to be
+-- recognized by the LogicalPlanner as a repartition join.
+-- Due to a three-way join this causes no valid path, besides the cartesian
+-- product on reference tables. This is allowed, so it should be able to be
+-- planned.
 SELECT *
 FROM
     test t1 JOIN test t2 USING (y), -- causes repartition, which makes this not routable or pushdownable
@@ -50,7 +53,19 @@ FROM
     ref b
 WHERE t2.y - a.a - b.b = 0
 ORDER BY 1,2,3;
-ERROR:  cannot perform distributed planning on this query
-DETAIL:  Cartesian products are currently unsupported
+ y | x | x | a | b | a | b 
+---+---+---+---+---+---+---
+(0 rows)
+
+-- The join clause is wider than it used to be, causing this query to be recognized by the LogicalPlanner as a repartition join.
+-- Unplannable query due to a three-way join which causes no valid path to be found
+SELECT *
+FROM
+    test t1 JOIN test t2 USING (y), -- causes repartition, which makes this not routable or pushdownable
+    test a,
+    test b
+WHERE t2.y - a.x - b.x = 0
+ORDER BY 1,2,3;
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
 SET client_min_messages TO WARNING;
 DROP SCHEMA expression_reference_join CASCADE;

src/test/regress/expected/multi_join_order_additional.out

@@ -99,9 +99,7 @@ LOG:  join order: [ "lineitem" ][ local partition join "orders" ]
 
 EXPLAIN SELECT l_quantity FROM lineitem, orders
 	WHERE (l_orderkey = o_orderkey OR l_quantity > 5);
-LOG:  join order: [ "lineitem" ][ cartesian product "orders" ]
-ERROR:  cannot perform distributed planning on this query
-DETAIL:  Cartesian products are currently unsupported
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
 EXPLAIN SELECT count(*) FROM orders, lineitem_hash
 	WHERE o_orderkey = l_orderkey;
 LOG:  join order: [ "orders" ][ single range partition join "lineitem_hash" ]

src/test/regress/expected/multi_mx_reference_table.out

@@ -846,16 +846,24 @@ LOG:  join order: [ "colocated_table_test" ][ reference join "reference_table_te
        2
 (2 rows)
 
+SET citus.enable_repartition_joins = on;
 SELECT
 	colocated_table_test.value_2
 FROM
 	reference_table_test, colocated_table_test, colocated_table_test_2
 WHERE
 	colocated_table_test.value_2 = reference_table_test.value_2
-ORDER BY 1;
-LOG:  join order: [ "colocated_table_test" ][ reference join "reference_table_test" ][ cartesian product "colocated_table_test_2" ]
-ERROR:  cannot perform distributed planning on this query
-DETAIL:  Cartesian products are currently unsupported
+ORDER BY colocated_table_test.value_2;
+LOG:  join order: [ "colocated_table_test_2" ][ cartesian product reference join "reference_table_test" ][ dual partition join "colocated_table_test" ]
+ value_2 
+---------
+       1
+       1
+       2
+       2
+(4 rows)
+
+RESET citus.enable_repartition_joins;
 SELECT
 	colocated_table_test.value_2
 FROM

src/test/regress/expected/multi_reference_table.out

@@ -1043,15 +1043,24 @@ LOG:  join order: [ "colocated_table_test" ][ reference join "reference_table_te
        2
 (2 rows)
 
+SET citus.enable_repartition_joins = on;
 SELECT
 	colocated_table_test.value_2
 FROM
 	reference_table_test, colocated_table_test, colocated_table_test_2
 WHERE
-	colocated_table_test.value_2 = reference_table_test.value_2;
-LOG:  join order: [ "colocated_table_test" ][ reference join "reference_table_test" ][ cartesian product "colocated_table_test_2" ]
-ERROR:  cannot perform distributed planning on this query
-DETAIL:  Cartesian products are currently unsupported
+	colocated_table_test.value_2 = reference_table_test.value_2
+ORDER BY colocated_table_test.value_2;
+LOG:  join order: [ "colocated_table_test_2" ][ cartesian product reference join "reference_table_test" ][ dual partition join "colocated_table_test" ]
+ value_2 
+---------
+       1
+       1
+       2
+       2
+(4 rows)
+
+RESET citus.enable_repartition_joins;
 SELECT
 	colocated_table_test.value_2
 FROM

src/test/regress/sql/expression_reference_join.sql

@@ -27,8 +27,11 @@ FROM
 WHERE t2.y * 2 = a.a
 ORDER BY 1,2,3;
 
--- The join clause is wider than it used to be, causing this query to be recognized by the LogicalPlanner as a repartition join.
--- Unplannable query due to a three-way join which causes no valid path (besides the cartesian product) to be found
+-- The join clause is wider than it used to be, causing this query to be
+-- recognized by the LogicalPlanner as a repartition join.
+-- Due to a three-way join this causes no valid path, besides the cartesian
+-- product on reference tables. This is allowed, so it should be able to be
+-- planned.
 SELECT *
 FROM
     test t1 JOIN test t2 USING (y), -- causes repartition, which makes this not routable or pushdownable
@@ -37,5 +40,17 @@ FROM
 WHERE t2.y - a.a - b.b = 0
 ORDER BY 1,2,3;
 
+
+-- The join clause is wider than it used to be, causing this query to be recognized by the LogicalPlanner as a repartition join.
+-- Unplannable query due to a three-way join which causes no valid path to be found
+SELECT *
+FROM
+    test t1 JOIN test t2 USING (y), -- causes repartition, which makes this not routable or pushdownable
+    test a,
+    test b
+WHERE t2.y - a.x - b.x = 0
+ORDER BY 1,2,3;
+
+
 SET client_min_messages TO WARNING;
 DROP SCHEMA expression_reference_join CASCADE;

src/test/regress/sql/multi_mx_reference_table.sql

@@ -518,13 +518,15 @@ WHERE
 ORDER BY 1;
 
 
+SET citus.enable_repartition_joins = on;
 SELECT
 	colocated_table_test.value_2
 FROM
 	reference_table_test, colocated_table_test, colocated_table_test_2
 WHERE
 	colocated_table_test.value_2 = reference_table_test.value_2
-ORDER BY 1;
+ORDER BY colocated_table_test.value_2;
+RESET citus.enable_repartition_joins;
 
 SELECT
 	colocated_table_test.value_2

src/test/regress/sql/multi_reference_table.sql

@@ -656,12 +656,15 @@ FROM
 WHERE
 	reference_table_test.value_1 = colocated_table_test.value_1;
 
+SET citus.enable_repartition_joins = on;
 SELECT
 	colocated_table_test.value_2
 FROM
 	reference_table_test, colocated_table_test, colocated_table_test_2
 WHERE
-	colocated_table_test.value_2 = reference_table_test.value_2;
+	colocated_table_test.value_2 = reference_table_test.value_2
+ORDER BY colocated_table_test.value_2;
+RESET citus.enable_repartition_joins;
 
 SELECT
 	colocated_table_test.value_2