Teach adjust_appendrel_attrs(_multilevel) to do multiple translations.

Currently, child relations are always base relations, so when we
translate parent relids to child relids, we only need to translate
a singler relid.  However, the proposed partition-wise join feature
will create child joins, which will mean we need to translate a set
of parent relids to the corresponding child relids.  This is
preliminary refactoring to make that possible.

Ashutosh Bapat.  Review and testing of the larger patch set of which
this is a part by Amit Langote, Rajkumar Raghuwanshi, Rafia Sabih,
Thomas Munro, Dilip Kumar, and me.  Some adjustments, mostly
cosmetic, by me.

Discussion: http://postgr.es/m/CA+TgmobQK80vtXjAsPZWWXd7c8u13G86gmuLupN+uUJjA+i4nA@mail.gmail.com

Author: robertmhaas

src/backend/optimizer/path/allpaths.c

@@ -942,7 +942,7 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 			Assert(IsA(rinfo, RestrictInfo));
 			childqual = adjust_appendrel_attrs(root,
 											   (Node *) rinfo->clause,
-											   appinfo);
+											   1, &appinfo);
 			childqual = eval_const_expressions(root, childqual);
 			/* check for flat-out constant */
 			if (childqual && IsA(childqual, Const))
@@ -1061,11 +1061,11 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 		childrel->joininfo = (List *)
 			adjust_appendrel_attrs(root,
 								   (Node *) rel->joininfo,
-								   appinfo);
+								   1, &appinfo);
 		childrel->reltarget->exprs = (List *)
 			adjust_appendrel_attrs(root,
 								   (Node *) rel->reltarget->exprs,
-								   appinfo);
+								   1, &appinfo);
 
 		/*
 		 * We have to make child entries in the EquivalenceClass data

src/backend/optimizer/path/equivclass.c

@@ -1329,7 +1329,8 @@ generate_join_implied_equalities_broken(PlannerInfo *root,
 	if (IS_OTHER_REL(inner_rel) && result != NIL)
 		result = (List *) adjust_appendrel_attrs_multilevel(root,
 															(Node *) result,
-															inner_rel);
+															inner_rel->relids,
+															inner_rel->top_parent_relids);
 
 	return result;
 }
@@ -2112,7 +2113,7 @@ add_child_rel_equivalences(PlannerInfo *root,
 				child_expr = (Expr *)
 					adjust_appendrel_attrs(root,
 										   (Node *) cur_em->em_expr,
-										   appinfo);
+										   1, &appinfo);
 
 				/*
 				 * Transform em_relids to match.  Note we do *not* do

src/backend/optimizer/plan/planner.c

@@ -1142,7 +1142,7 @@ inheritance_planner(PlannerInfo *root)
 		subroot->parse = (Query *)
 			adjust_appendrel_attrs(root,
 								   (Node *) parse,
-								   appinfo);
+								   1, &appinfo);
 
 		/*
 		 * If there are securityQuals attached to the parent, move them to the