Some preliminary refactoring towards partitionwise join.

Partitionwise join proposes add a concept of child join relations,
which will have the same relationship with join relations as "other
member" relations do with base relations.  These relations will need
some but not all of the handling that we currently have for join
relations, and some but not all of the handling that we currently have
for appendrels, since they are a mix of the two.  Refactor a little
bit so that the necessary bits of logic are exposed as separate
functions.

Ashutosh Bapat, reviewed and tested by Rajkumar Raghuwanshi and
by me.

Discussion: http://postgr.es/m/CAFjFpRfqotRR6cM3sooBHMHEVdkFfAZ6PyYg4GRZsoMuW08HjQ@mail.gmail.com

1 files changed, 42 insertions, 10 deletions

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 4db1d16c790..43bfd23804c 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -129,6 +129,8 @@ static void subquery_push_qual(Query *subquery,
 static void recurse_push_qual(Node *setOp, Query *topquery,
 				  RangeTblEntry *rte, Index rti, Node *qual);
 static void remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel);
+static void add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
+						List *live_childrels);
 
 
 /*
@@ -1182,19 +1184,11 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 {
 	int			parentRTindex = rti;
 	List	   *live_childrels = NIL;
-	List	   *subpaths = NIL;
-	bool		subpaths_valid = true;
-	List	   *partial_subpaths = NIL;
-	bool		partial_subpaths_valid = true;
-	List	   *all_child_pathkeys = NIL;
-	List	   *all_child_outers = NIL;
 	ListCell   *l;
 
 	/*
 	 * Generate access paths for each member relation, and remember the
-	 * cheapest path for each one.  Also, identify all pathkeys (orderings)
-	 * and parameterizations (required_outer sets) available for the member
-	 * relations.
+	 * non-dummy children.
 	 */
 	foreach(l, root->append_rel_list)
 	{
@@ -1202,7 +1196,6 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 		int			childRTindex;
 		RangeTblEntry *childRTE;
 		RelOptInfo *childrel;
-		ListCell   *lcp;
 
 		/* append_rel_list contains all append rels; ignore others */
 		if (appinfo->parent_relid != parentRTindex)
@@ -1237,6 +1230,45 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 		 * Child is live, so add it to the live_childrels list for use below.
 		 */
 		live_childrels = lappend(live_childrels, childrel);
+	}
+
+	/* Add paths to the "append" relation. */
+	add_paths_to_append_rel(root, rel, live_childrels);
+}
+
+
+/*
+ * add_paths_to_append_rel
+ *		Generate paths for given "append" relation given the set of non-dummy
+ *		child rels.
+ *
+ * The function collects all parameterizations and orderings supported by the
+ * non-dummy children. For every such parameterization or ordering, it creates
+ * an append path collecting one path from each non-dummy child with given
+ * parameterization or ordering. Similarly it collects partial paths from
+ * non-dummy children to create partial append paths.
+ */
+static void
+add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
+						List *live_childrels)
+{
+	List	   *subpaths = NIL;
+	bool		subpaths_valid = true;
+	List	   *partial_subpaths = NIL;
+	bool		partial_subpaths_valid = true;
+	List	   *all_child_pathkeys = NIL;
+	List	   *all_child_outers = NIL;
+	ListCell   *l;
+
+	/*
+	 * For every non-dummy child, remember the cheapest path.  Also, identify
+	 * all pathkeys (orderings) and parameterizations (required_outer sets)
+	 * available for the non-dummy member relations.
+	 */
+	foreach(l, live_childrels)
+	{
+		RelOptInfo *childrel = lfirst(l);
+		ListCell   *lcp;
 
 		/*
 		 * If child has an unparameterized cheapest-total path, add that to