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, 83 insertions, 59 deletions

diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index caf8291e106..6ab78545c36 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -49,6 +49,9 @@ static List *subbuild_joinrel_restrictlist(RelOptInfo *joinrel,
 static List *subbuild_joinrel_joinlist(RelOptInfo *joinrel,
 						  List *joininfo_list,
 						  List *new_joininfo);
+static void set_foreign_rel_properties(RelOptInfo *joinrel,
+						   RelOptInfo *outer_rel, RelOptInfo *inner_rel);
+static void add_join_rel(PlannerInfo *root, RelOptInfo *joinrel);
 
 
 /*
@@ -328,6 +331,82 @@ find_join_rel(PlannerInfo *root, Relids relids)
 }
 
 /*
+ * set_foreign_rel_properties
+ *		Set up foreign-join fields if outer and inner relation are foreign
+ *		tables (or joins) belonging to the same server and assigned to the same
+ *		user to check access permissions as.
+ *
+ * In addition to an exact match of userid, we allow the case where one side
+ * has zero userid (implying current user) and the other side has explicit
+ * userid that happens to equal the current user; but in that case, pushdown of
+ * the join is only valid for the current user.  The useridiscurrent field
+ * records whether we had to make such an assumption for this join or any
+ * sub-join.
+ *
+ * Otherwise these fields are left invalid, so GetForeignJoinPaths will not be
+ * called for the join relation.
+ *
+ */
+static void
+set_foreign_rel_properties(RelOptInfo *joinrel, RelOptInfo *outer_rel,
+						   RelOptInfo *inner_rel)
+{
+	if (OidIsValid(outer_rel->serverid) &&
+		inner_rel->serverid == outer_rel->serverid)
+	{
+		if (inner_rel->userid == outer_rel->userid)
+		{
+			joinrel->serverid = outer_rel->serverid;
+			joinrel->userid = outer_rel->userid;
+			joinrel->useridiscurrent = outer_rel->useridiscurrent || inner_rel->useridiscurrent;
+			joinrel->fdwroutine = outer_rel->fdwroutine;
+		}
+		else if (!OidIsValid(inner_rel->userid) &&
+				 outer_rel->userid == GetUserId())
+		{
+			joinrel->serverid = outer_rel->serverid;
+			joinrel->userid = outer_rel->userid;
+			joinrel->useridiscurrent = true;
+			joinrel->fdwroutine = outer_rel->fdwroutine;
+		}
+		else if (!OidIsValid(outer_rel->userid) &&
+				 inner_rel->userid == GetUserId())
+		{
+			joinrel->serverid = outer_rel->serverid;
+			joinrel->userid = inner_rel->userid;
+			joinrel->useridiscurrent = true;
+			joinrel->fdwroutine = outer_rel->fdwroutine;
+		}
+	}
+}
+
+/*
+ * add_join_rel
+ *		Add given join relation to the list of join relations in the given
+ *		PlannerInfo. Also add it to the auxiliary hashtable if there is one.
+ */
+static void
+add_join_rel(PlannerInfo *root, RelOptInfo *joinrel)
+{
+	/* GEQO requires us to append the new joinrel to the end of the list! */
+	root->join_rel_list = lappend(root->join_rel_list, joinrel);
+
+	/* store it into the auxiliary hashtable if there is one. */
+	if (root->join_rel_hash)
+	{
+		JoinHashEntry *hentry;
+		bool		found;
+
+		hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
+											   &(joinrel->relids),
+											   HASH_ENTER,
+											   &found);
+		Assert(!found);
+		hentry->join_rel = joinrel;
+	}
+}
+
+/*
  * build_join_rel
  *	  Returns relation entry corresponding to the union of two given rels,
  *	  creating a new relation entry if none already exists.
@@ -425,46 +504,8 @@ build_join_rel(PlannerInfo *root,
 	joinrel->joininfo = NIL;
 	joinrel->has_eclass_joins = false;
 
-	/*
-	 * Set up foreign-join fields if outer and inner relation are foreign
-	 * tables (or joins) belonging to the same server and assigned to the same
-	 * user to check access permissions as.  In addition to an exact match of
-	 * userid, we allow the case where one side has zero userid (implying
-	 * current user) and the other side has explicit userid that happens to
-	 * equal the current user; but in that case, pushdown of the join is only
-	 * valid for the current user.  The useridiscurrent field records whether
-	 * we had to make such an assumption for this join or any sub-join.
-	 *
-	 * Otherwise these fields are left invalid, so GetForeignJoinPaths will
-	 * not be called for the join relation.
-	 */
-	if (OidIsValid(outer_rel->serverid) &&
-		inner_rel->serverid == outer_rel->serverid)
-	{
-		if (inner_rel->userid == outer_rel->userid)
-		{
-			joinrel->serverid = outer_rel->serverid;
-			joinrel->userid = outer_rel->userid;
-			joinrel->useridiscurrent = outer_rel->useridiscurrent || inner_rel->useridiscurrent;
-			joinrel->fdwroutine = outer_rel->fdwroutine;
-		}
-		else if (!OidIsValid(inner_rel->userid) &&
-				 outer_rel->userid == GetUserId())
-		{
-			joinrel->serverid = outer_rel->serverid;
-			joinrel->userid = outer_rel->userid;
-			joinrel->useridiscurrent = true;
-			joinrel->fdwroutine = outer_rel->fdwroutine;
-		}
-		else if (!OidIsValid(outer_rel->userid) &&
-				 inner_rel->userid == GetUserId())
-		{
-			joinrel->serverid = outer_rel->serverid;
-			joinrel->userid = inner_rel->userid;
-			joinrel->useridiscurrent = true;
-			joinrel->fdwroutine = outer_rel->fdwroutine;
-		}
-	}
+	/* Compute information relevant to the foreign relations. */
+	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
 	/*
 	 * Create a new tlist containing just the vars that need to be output from
@@ -532,25 +573,8 @@ build_join_rel(PlannerInfo *root,
 		is_parallel_safe(root, (Node *) joinrel->reltarget->exprs))
 		joinrel->consider_parallel = true;
 
-	/*
-	 * Add the joinrel to the query's joinrel list, and store it into the
-	 * auxiliary hashtable if there is one.  NB: GEQO requires us to append
-	 * the new joinrel to the end of the list!
-	 */
-	root->join_rel_list = lappend(root->join_rel_list, joinrel);
-
-	if (root->join_rel_hash)
-	{
-		JoinHashEntry *hentry;
-		bool		found;
-
-		hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
-											   &(joinrel->relids),
-											   HASH_ENTER,
-											   &found);
-		Assert(!found);
-		hentry->join_rel = joinrel;
-	}
+	/* Add the joinrel to the PlannerInfo. */
+	add_join_rel(root, joinrel);
 
 	/*
 	 * Also, if dynamic-programming join search is active, add the new joinrel