Check if the outer table has distribution column, wip, still need to check the using clause or join constraint

src/backend/distributed/planner/deparse_shard_query.c

@@ -291,6 +291,7 @@ UpdateWhereClauseForOuterJoin(Node *node, List *relationShardList)
 	* distributed tables in the join clause.
 	*/
 	RangeTblEntry *innerRte = NULL;
+	RangeTblEntry *outerRte = NULL;
 	int outerRtIndex = -1;
 	bool result = ExtractIndexesForConstaints(fromExpr->fromlist, query->rtable, &outerRtIndex, &innerRte);
 	if (!result)
@@ -310,11 +311,25 @@ UpdateWhereClauseForOuterJoin(Node *node, List *relationShardList)
 	Var *partitionColumnVar = cacheEntry->partitionColumn;
 
 	/* 
-	* we will add constraints for the outer table, so we need to set the varno
+	* we will add constraints for the outer table, we need to find the column in the outer 
-	* TODO: this only works when the outer table has the distribution column,
+	* table that is comparable to the partition column of the inner table.
-	* we shoul not end up here if this is not the case.
+	* If the column does not exist, we return without modifying the query.
+	* If the column exists, we create a Var node for the outer table's partition column.
 	*/
-	partitionColumnVar->varno = outerRtIndex;
+	outerRte = rt_fetch(outerRtIndex, query->rtable);
+	AttrNumber attnum = GetAttrNumForMatchingColumn(outerRte, relationId, partitionColumnVar);
+	// TODO: we also have to check that the tables are joined on the partition column. 
+	if( attnum == InvalidAttrNumber)
+	{
+		return query_tree_walker(query, UpdateWhereClauseForOuterJoin, relationShardList, 0);
+	}
+
+	Var* outerTablePartitionColumnVar = makeVar(
+					outerRtIndex, attnum, partitionColumnVar->vartype,
+					partitionColumnVar->vartypmod,
+					partitionColumnVar->varcollid,
+					0);
+
 	bool isFirstShard = IsFirstShard(cacheEntry, shardId);
 	
 	/* load the interval for the shard and create constant nodes for the upper/lower bounds */
@@ -327,7 +342,7 @@ UpdateWhereClauseForOuterJoin(Node *node, List *relationShardList)
 	/* create a function expression node for the hash partition column */ 
 	FuncExpr *hashFunction = makeNode(FuncExpr);
 	hashFunction->funcid = cacheEntry->hashFunction->fn_oid;
-	hashFunction->args = list_make1(partitionColumnVar);
+	hashFunction->args = list_make1(outerTablePartitionColumnVar);
 	hashFunction->funcresulttype = get_func_rettype(cacheEntry->hashFunction->fn_oid);
 	hashFunction->funcretset = false;
 

src/backend/distributed/planner/recursive_planning.c

@@ -756,6 +756,7 @@ RecursivelyPlanRecurringTupleOuterJoinWalker(Node *node, Query *query,
 					int outerRtIndex = ((RangeTblRef *) leftNode)->rtindex;
 					RangeTblEntry *rte = rt_fetch(outerRtIndex, query->rtable);
 					RangeTblEntry *innerRte = NULL;
+					bool planned = false;
 					if (!IsPushdownSafeForRTEInLeftJoin(rte))
 					{
 						ereport(DEBUG1, (errmsg("recursively planning right side of "
@@ -763,6 +764,7 @@ RecursivelyPlanRecurringTupleOuterJoinWalker(Node *node, Query *query,
 												"is a recurring rel that is not an RTE")));
 						RecursivelyPlanDistributedJoinNode(rightNode, query,
 														   recursivePlanningContext);
+						planned = true;
 					}
 					else if (!CheckIfAllCitusRTEsAreColocated(rightNode, query->rtable, &innerRte))
 					{
@@ -771,7 +773,26 @@ RecursivelyPlanRecurringTupleOuterJoinWalker(Node *node, Query *query,
 												"join are not colocated")));
 						RecursivelyPlanDistributedJoinNode(rightNode, query,
 									                       recursivePlanningContext);
+						planned = true;					
 					}
+
+					if(!planned)
+					{
+						CitusTableCacheEntry *cacheEntry = GetCitusTableCacheEntry(innerRte->relid)
+						if(GetAttrNumForMatchingColumn(rte, innerRte->relid, cacheEntry->partitionColumn) == InvalidAttrNumber)
+						{
+							ereport(DEBUG1, (errmsg("recursively planning right side of the left join "
+													"since the outer side does not have the distribution column")));
+							RecursivelyPlanDistributedJoinNode(rightNode, query, recursivePlanningContext);
+						}
+						else
+						{
+							ereport(DEBUG1, (errmsg("not recursively planning right side of the left join "
+													"since the outer side is a RangeTblRef and "
+													"the inner side is colocated with it")));
+						}
+					}
+
 				}
 				/*
 				* rightNodeRecurs if there is a recurring table in the right side. However, if the right side 

src/backend/distributed/utils/query_utils.c

@@ -21,6 +21,7 @@
 #include "distributed/query_utils.h"
 #include "distributed/relation_restriction_equivalence.h"
 #include "distributed/version_compat.h"
+#include "utils/lsyscache.h"
 
 
 static bool CitusQueryableRangeTableRelation(RangeTblEntry *rangeTableEntry);
@@ -239,7 +240,8 @@ ExtractRangeTableIds(Node *node, ExtractRangeTableIdsContext *context)
  * given node are colocated. If they are, it sets the value of rte to a
  * representative table.
  */
-bool CheckIfAllCitusRTEsAreColocated(Node *node, List *rtable, RangeTblEntry **rte)
+bool
+CheckIfAllCitusRTEsAreColocated(Node *node, List *rtable, RangeTblEntry **rte)
 {
 	ExtractRangeTableIdsContext context;
 	List *idList = NIL;
@@ -268,5 +270,29 @@ bool CheckIfAllCitusRTEsAreColocated(Node *node, List *rtable, RangeTblEntry **r
 	}
 
 	return true;
-
+}
+
+/*
+ * GetAttrNumForMatchingColumn returns the attribute number for the column
+ * in the target relation that matches the given Var. If the column does not
+ * exist or is not comparable, it returns InvalidAttrNumber.
+ */
+AttrNumber
+GetAttrNumForMatchingColumn(RangeTblEntry *rteTarget, Oid relid, Var *var)
+{
+	char *targetColumnName = get_attname(relid, var->varattno, false);
+	AttrNumber attnum = get_attnum(rteTarget->relid, targetColumnName);
+	if (attnum == InvalidAttrNumber)
+	{
+		ereport(DEBUG5, (errmsg("Column %s does not exist in relation %s",
+							   targetColumnName, rteTarget->eref->aliasname)));
+		return InvalidAttrNumber;
+	}
+	if(var->vartype != get_atttype(rteTarget->relid, attnum))
+	{
+		ereport(DEBUG5, (errmsg("Column %s is not comparable for tables with relids %d and %d",
+							   targetColumnName, rteTarget->relid, relid)));
+		return InvalidAttrNumber;
+	}
+	return attnum;
 }

src/include/distributed/query_utils.h

@@ -47,4 +47,5 @@ extern bool ExtractRangeTableEntryWalker(Node *node, List **rangeTableList);
 extern bool ExtractRangeTableIndexWalker(Node *node, List **rangeTableIndexList);
 extern bool ExtractRangeTableIds(Node *node, ExtractRangeTableIdsContext *context);
 extern bool CheckIfAllCitusRTEsAreColocated(Node *node, List *rtable, RangeTblEntry **rte);
+AttrNumber GetAttrNumForMatchingColumn(RangeTblEntry *rteTarget, Oid relid, Var *var);
 #endif /* QUERY_UTILS_H */