hacky hack for double distributed join

src/backend/distributed/planner/distributed_planner.c

@@ -1749,8 +1749,40 @@ multi_join_restriction_hook(PlannerInfo *root,
 }
 
 
+static Node *
+VarNoMutator(Node *expr, Index *varno)
+{
+	switch (nodeTag(expr))
+	{
+		case T_Var:
+		{
+			Var *var = castNode(Var, expr);
+			if (var->varno == *varno)
+			{
+				/*nothing to change */
+				return (Node *) var;
+			}
+
+			return (Node *) makeVar(
+				*varno,
+				var->varattno,
+				var->vartype,
+				var->vartypmod,
+				var->varcollid,
+				var->varlevelsup
+			);
+		}
+
+		default:
+		{
+			return expression_tree_mutator(expr, (void*) VarNoMutator, varno);
+		}
+	}
+}
+
+
 static Query *
-GetQueryFromPath(List *tlist, RangeTblEntry *rte)
+GetQueryFromPath(List *tlist, RangeTblEntry *rte, List *clauses)
 {
 	Query *q = makeNode(Query);
 	q->commandType = CMD_SELECT;
@@ -1760,20 +1792,8 @@ GetQueryFromPath(List *tlist, RangeTblEntry *rte)
 	TargetEntry *target = NULL;
 	foreach_ptr(target, tlist)
 	{
-		Var *var = castNode(Var, target->expr);
+		Index varno = 1;
-		TargetEntry *newTarget = makeTargetEntry(
+		TargetEntry *newTarget = (TargetEntry *) VarNoMutator((Node *)target, &varno);
-			(Expr *) makeVar(
-				1,
-				var->varattno,
-				var->vartype,
-				var->vartypmod,
-				var->varcollid,
-				var->varlevelsup
-			),
-			target->resno,
-			target->resname,
-			target->resjunk
-		);
 		newTargetList = lappend(newTargetList, newTarget);
 	}
 
@@ -1782,6 +1802,19 @@ GetQueryFromPath(List *tlist, RangeTblEntry *rte)
 	RangeTblRef *rr = makeNode(RangeTblRef);
 	rr->rtindex = 1;
 	q->jointree->fromlist = list_make1(rr);
+
+	List *quals = NIL;
+
+	RestrictInfo *rinfo = NULL;
+	foreach_ptr(rinfo, clauses)
+	{
+		Node *clause = (Node *) rinfo->clause;
+		Index varno = 1;
+		clause = VarNoMutator(clause, &varno);
+		quals = lappend(quals, clause);
+	}
+	q->jointree->quals = (Node *) quals;
+
 	return q;
 }
 
@@ -1794,6 +1827,7 @@ VarnoFromFirstTargetEntry(List *tlist)
 	return var->varno;
 }
 
+#include "optimizer/restrictinfo.h"
 
 static Plan *
 CreateDistributedUnionPlan(PlannerInfo *root,
@@ -1807,10 +1841,11 @@ CreateDistributedUnionPlan(PlannerInfo *root,
 	workerJob->jobId = UniqueJobId();
 
 	RangeTblEntry *rte = list_nth_node(RangeTblEntry, best_path->custom_private, 0);
+	Path *originalPath = (Path *) list_nth(best_path->custom_private, 1);
 	List* shardIntervalList = LoadShardIntervalList(rte->relid);
 	ShardInterval *shardInterval = NULL;
 
-	Query *q = GetQueryFromPath(tlist, rte);
+	Query *q = GetQueryFromPath(tlist, rte, clauses);
 
 	int i = 0;
 	foreach_ptr(shardInterval, shardIntervalList)
@@ -1846,6 +1881,11 @@ CreateDistributedUnionPlan(PlannerInfo *root,
 	plan->custom_private = list_make1(distributedPlan);
 
 	plan->scan.plan.targetlist = tlist;
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	clauses = extract_actual_clauses(clauses, false);
+
+	plan->scan.plan.qual = clauses;
+	plan->custom_exprs = clauses;
 
 	return (Plan *) plan;
 }
@@ -1876,8 +1916,8 @@ WrapTableAccessWithDistributedUnion(Path *originalPath, RangeTblEntry *rte)
 
 	/* TODO use a better cost model */
 	distUnion->path.rows = originalPath->rows;
-	distUnion->path.startup_cost = originalPath->startup_cost;
+	distUnion->path.startup_cost = originalPath->startup_cost+1000;
-	distUnion->path.total_cost = originalPath->total_cost;
+	distUnion->path.total_cost = originalPath->total_cost+1000;
 
 	distUnion->methods = &distributedUnionMethods;