Abstract logic to allow for multiple kinds of child rels.

Currently, the only type of child relation is an "other member rel",
which is the child of a baserel, but in the future joins and even
upper relations may have child rels.  To facilitate that, introduce
macros that test to test for particular RelOptKind values, and use
them in various places where they help to clarify the sense of a test.
(For example, a test may allow RELOPT_OTHER_MEMBER_REL either because
it intends to allow child rels, or because it intends to allow simple
rels.)

Also, remove find_childrel_top_parent, which will not work for a
child rel that is not a baserel.  Instead, add a new RelOptInfo
member top_parent_relids to track the same kind of information in a
more generic manner.

Ashutosh Bapat, slightly tweaked by me.  Review and testing of the
patch set from which this was taken by Rajkumar Raghuwanshi and Rafia
Sabih.

Discussion: http://postgr.es/m/CA+TgmoagTnF2yqR3PT2rv=om=wJiZ4-A+ATwdnriTGku1CLYxA@mail.gmail.com

src/backend/optimizer/path/allpaths.c

@@ -539,8 +539,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
 	Assert(root->glob->parallelModeOK);
 
 	/* This should only be called for baserels and appendrel children. */
-	Assert(rel->reloptkind == RELOPT_BASEREL ||
-		   rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
+	Assert(IS_SIMPLE_REL(rel));
 
 	/* Assorted checks based on rtekind. */
 	switch (rte->rtekind)
@@ -846,7 +845,7 @@ set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 
 /*
  * set_append_rel_size
- *	  Set size estimates for an "append relation"
+ *	  Set size estimates for a simple "append relation"
  *
  * The passed-in rel and RTE represent the entire append relation.  The
  * relation's contents are computed by appending together the output of
@@ -867,6 +866,8 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 	int			nattrs;
 	ListCell   *l;
 
+	Assert(IS_SIMPLE_REL(rel));
+
 	/*
 	 * Initialize to compute size estimates for whole append relation.
 	 *

src/backend/optimizer/path/equivclass.c

@@ -1060,10 +1060,12 @@ generate_join_implied_equalities_for_ecs(PlannerInfo *root,
 	ListCell   *lc;
 
 	/* If inner rel is a child, extra setup work is needed */
-	if (inner_rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
+	if (IS_OTHER_REL(inner_rel))
 	{
+		Assert(!bms_is_empty(inner_rel->top_parent_relids));
+
 		/* Fetch relid set for the topmost parent rel */
-		nominal_inner_relids = find_childrel_top_parent(root, inner_rel)->relids;
+		nominal_inner_relids = inner_rel->top_parent_relids;
 		/* ECs will be marked with the parent's relid, not the child's */
 		nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
 	}
@@ -1324,8 +1326,7 @@ generate_join_implied_equalities_broken(PlannerInfo *root,
 	 * mentioned in the ec_sources clauses, we have to be prepared to apply
 	 * multiple levels of Var translation.
 	 */
-	if (inner_rel->reloptkind == RELOPT_OTHER_MEMBER_REL &&
-		result != NIL)
+	if (IS_OTHER_REL(inner_rel) && result != NIL)
 		result = (List *) adjust_appendrel_attrs_multilevel(root,
 															(Node *) result,
 															inner_rel);
@@ -2180,6 +2181,9 @@ generate_implied_equalities_for_column(PlannerInfo *root,
 	Relids		parent_relids;
 	ListCell   *lc1;
 
+	/* Indexes are available only on base or "other" member relations. */
+	Assert(IS_SIMPLE_REL(rel));
+
 	/* If it's a child rel, we'll need to know what its parent(s) are */
 	if (is_child_rel)
 		parent_relids = find_childrel_parents(root, rel);
@@ -2413,8 +2417,11 @@ eclass_useful_for_merging(PlannerInfo *root,
 	 */
 
 	/* If specified rel is a child, we must consider the topmost parent rel */
-	if (rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
-		relids = find_childrel_top_parent(root, rel)->relids;
+	if (IS_OTHER_REL(rel))
+	{
+		Assert(!bms_is_empty(rel->top_parent_relids));
+		relids = rel->top_parent_relids;
+	}
 	else
 		relids = rel->relids;
 

src/backend/optimizer/path/indxpath.c

@@ -2779,6 +2779,9 @@ check_index_predicates(PlannerInfo *root, RelOptInfo *rel)
 	Relids		otherrels;
 	ListCell   *lc;
 
+	/* Indexes are available only on base or "other" member relations. */
+	Assert(IS_SIMPLE_REL(rel));
+
 	/*
 	 * Initialize the indrestrictinfo lists to be identical to
 	 * baserestrictinfo, and check whether there are any partial indexes.  If

src/backend/optimizer/plan/createplan.c

@@ -3461,7 +3461,7 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
 	 * upper rel doesn't have relids set, but it covers all the base relations
 	 * participating in the underlying scan, so use root's all_baserels.
 	 */
-	if (rel->reloptkind == RELOPT_UPPER_REL)
+	if (IS_UPPER_REL(rel))
 		scan_plan->fs_relids = root->all_baserels;
 	else
 		scan_plan->fs_relids = best_path->path.parent->relids;

src/backend/optimizer/plan/initsplan.c

@@ -109,7 +109,7 @@ add_base_rels_to_query(PlannerInfo *root, Node *jtnode)
 	{
 		int			varno = ((RangeTblRef *) jtnode)->rtindex;
 
-		(void) build_simple_rel(root, varno, RELOPT_BASEREL);
+		(void) build_simple_rel(root, varno, NULL);
 	}
 	else if (IsA(jtnode, FromExpr))
 	{

src/backend/optimizer/plan/planmain.c

@@ -242,8 +242,7 @@ query_planner(PlannerInfo *root, List *tlist,
 
 		Assert(brel->relid == rti);		/* sanity check on array */
 
-		if (brel->reloptkind == RELOPT_BASEREL ||
-			brel->reloptkind == RELOPT_OTHER_MEMBER_REL)
+		if (IS_SIMPLE_REL(brel))
 			total_pages += (double) brel->pages;
 	}
 	root->total_table_pages = total_pages;

src/backend/optimizer/plan/planner.c

@@ -6001,7 +6001,7 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
 	setup_simple_rel_arrays(root);
 
 	/* Build RelOptInfo */
-	rel = build_simple_rel(root, 1, RELOPT_BASEREL);
+	rel = build_simple_rel(root, 1, NULL);
 
 	/* Locate IndexOptInfo for the target index */
 	indexInfo = NULL;

src/backend/optimizer/prep/prepunion.c

@@ -271,7 +271,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
 		 * used for much here, but it carries the subroot data structures
 		 * forward to setrefs.c processing.
 		 */
-		rel = build_simple_rel(root, rtr->rtindex, RELOPT_BASEREL);
+		rel = build_simple_rel(root, rtr->rtindex, NULL);
 
 		/* plan_params should not be in use in current query level */
 		Assert(root->plan_params == NIL);
@@ -2143,7 +2143,7 @@ adjust_appendrel_attrs_multilevel(PlannerInfo *root, Node *node,
 	RelOptInfo *parent_rel = find_base_rel(root, appinfo->parent_relid);
 
 	/* If parent is also a child, first recurse to apply its translations */
-	if (parent_rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
+	if (IS_OTHER_REL(parent_rel))
 		node = adjust_appendrel_attrs_multilevel(root, node, parent_rel);
 	else
 		Assert(parent_rel->reloptkind == RELOPT_BASEREL);

src/backend/optimizer/util/plancat.c

@@ -1337,6 +1337,9 @@ relation_excluded_by_constraints(PlannerInfo *root,
 	List	   *safe_constraints;
 	ListCell   *lc;
 
+	/* As of now, constraint exclusion works only with simple relations. */
+	Assert(IS_SIMPLE_REL(rel));
+
 	/*
 	 * Regardless of the setting of constraint_exclusion, detect
 	 * constant-FALSE-or-NULL restriction clauses.  Because const-folding will

src/backend/optimizer/util/relnode.c

@@ -88,7 +88,7 @@ setup_simple_rel_arrays(PlannerInfo *root)
  *	  Construct a new RelOptInfo for a base relation or 'other' relation.
  */
 RelOptInfo *
-build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
+build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 {
 	RelOptInfo *rel;
 	RangeTblEntry *rte;
@@ -103,7 +103,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	Assert(rte != NULL);
 
 	rel = makeNode(RelOptInfo);
-	rel->reloptkind = reloptkind;
+	rel->reloptkind = parent ? RELOPT_OTHER_MEMBER_REL : RELOPT_BASEREL;
 	rel->relids = bms_make_singleton(relid);
 	rel->rows = 0;
 	/* cheap startup cost is interesting iff not all tuples to be retrieved */
@@ -144,6 +144,22 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	rel->joininfo = NIL;
 	rel->has_eclass_joins = false;
 
+	/*
+	 * Pass top parent's relids down the inheritance hierarchy. If the parent
+	 * has top_parent_relids set, it's a direct or an indirect child of the top
+	 * parent indicated by top_parent_relids. By extention this child is also
+	 * an indirect child of that parent.
+	 */
+	if (parent)
+	{
+		if (parent->top_parent_relids)
+			rel->top_parent_relids = parent->top_parent_relids;
+		else
+			rel->top_parent_relids = bms_copy(parent->relids);
+	}
+	else
+		rel->top_parent_relids = NULL;
+
 	/* Check type of rtable entry */
 	switch (rte->rtekind)
 	{
@@ -209,7 +225,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 				continue;
 
 			(void) build_simple_rel(root, appinfo->child_relid,
-									RELOPT_OTHER_MEMBER_REL);
+									rel);
 		}
 	}
 
@@ -504,6 +520,7 @@ build_join_rel(PlannerInfo *root,
 	joinrel->baserestrict_min_security = UINT_MAX;
 	joinrel->joininfo = NIL;
 	joinrel->has_eclass_joins = false;
+	joinrel->top_parent_relids = NULL;
 
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
@@ -965,32 +982,6 @@ find_childrel_appendrelinfo(PlannerInfo *root, RelOptInfo *rel)
 }
 
 
-/*
- * find_childrel_top_parent
- *		Fetch the topmost appendrel parent rel of an appendrel child rel.
- *
- * Since appendrels can be nested, a child could have multiple levels of
- * appendrel ancestors.  This function locates the topmost ancestor,
- * which will be a regular baserel not an otherrel.
- */
-RelOptInfo *
-find_childrel_top_parent(PlannerInfo *root, RelOptInfo *rel)
-{
-	do
-	{
-		AppendRelInfo *appinfo = find_childrel_appendrelinfo(root, rel);
-		Index		prelid = appinfo->parent_relid;
-
-		/* traverse up to the parent rel, loop if it's also a child rel */
-		rel = find_base_rel(root, prelid);
-	} while (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
-
-	Assert(rel->reloptkind == RELOPT_BASEREL);
-
-	return rel;
-}
-
-
 /*
  * find_childrel_parents
  *		Compute the set of parent relids of an appendrel child rel.
@@ -1004,6 +995,8 @@ find_childrel_parents(PlannerInfo *root, RelOptInfo *rel)
 {
 	Relids		result = NULL;
 
+	Assert(rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
+
 	do
 	{
 		AppendRelInfo *appinfo = find_childrel_appendrelinfo(root, rel);