Do assorted mop-up in the planner.

Remove RestrictInfo.nullable_relids, along with a good deal of
infrastructure that calculated it.  One use-case for it was in
join_clause_is_movable_to, but we can now replace that usage with
a check to see if the clause's relids include any outer join
that can null the target relation.  The other use-case was in
join_clause_is_movable_into, but that test can just be dropped
entirely now that the clause's relids include outer joins.
Furthermore, join_clause_is_movable_into should now be
accurate enough that it will accept anything returned by
generate_join_implied_equalities, so we can restore the Assert
that was diked out in commit 95f4e59c3.

Remove the outerjoin_delayed mechanism.  We needed this before to
prevent quals from getting evaluated below outer joins that should
null some of their vars.  Now that we consider varnullingrels while
placing quals, that's taken care of automatically, so throw the
whole thing away.

Teach remove_useless_result_rtes to also remove useless FromExprs.
Having done that, the delay_upper_joins flag serves no purpose any
more and we can remove it, largely reverting 11086f2f2.

Use constant TRUE for "dummy" clauses when throwing back outer joins.
This improves on a hack I introduced in commit 6a6522529.  If we
have a left-join clause l.x = r.y, and a WHERE clause l.x = constant,
we generate r.y = constant and then don't really have a need for the
join clause.  But we must throw the join clause back anyway after
marking it redundant, so that the join search heuristics won't think
this is a clauseless join and avoid it.  That was a kluge introduced
under time pressure, and after looking at it I thought of a better
way: let's just introduce constant-TRUE "join clauses" instead,
and get rid of them at the end.  This improves the generated plans for
such cases by not having to test a redundant join clause.  We can also
get rid of the ugly hack used to mark such clauses as redundant for
selectivity estimation.

Patch by me; thanks to Richard Guo for review.

Discussion: https://postgr.es/m/830269.1656693747@sss.pgh.pa.us

1 files changed, 7 insertions, 33 deletions

diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index d2e241c983c..c4e7f97f687 100644
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -180,9 +180,6 @@ pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys)
  *	  Given an expression and sort-order information, create a PathKey.
  *	  The result is always a "canonical" PathKey, but it might be redundant.
  *
- * expr is the expression, and nullable_relids is the set of base relids
- * that are potentially nullable below it.
- *
  * If the PathKey is being generated from a SortGroupClause, sortref should be
  * the SortGroupClause's SortGroupRef; otherwise zero.
  *
@@ -198,7 +195,6 @@ pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys)
 static PathKey *
 make_pathkey_from_sortinfo(PlannerInfo *root,
 						   Expr *expr,
-						   Relids nullable_relids,
 						   Oid opfamily,
 						   Oid opcintype,
 						   Oid collation,
@@ -234,7 +230,7 @@ make_pathkey_from_sortinfo(PlannerInfo *root,
 			 equality_op);
 
 	/* Now find or (optionally) create a matching EquivalenceClass */
-	eclass = get_eclass_for_sort_expr(root, expr, nullable_relids,
+	eclass = get_eclass_for_sort_expr(root, expr,
 									  opfamilies, opcintype, collation,
 									  sortref, rel, create_it);
 
@@ -257,7 +253,6 @@ make_pathkey_from_sortinfo(PlannerInfo *root,
 static PathKey *
 make_pathkey_from_sortop(PlannerInfo *root,
 						 Expr *expr,
-						 Relids nullable_relids,
 						 Oid ordering_op,
 						 bool nulls_first,
 						 Index sortref,
@@ -279,7 +274,6 @@ make_pathkey_from_sortop(PlannerInfo *root,
 
 	return make_pathkey_from_sortinfo(root,
 									  expr,
-									  nullable_relids,
 									  opfamily,
 									  opcintype,
 									  collation,
@@ -584,12 +578,10 @@ build_index_pathkeys(PlannerInfo *root,
 		}
 
 		/*
-		 * OK, try to make a canonical pathkey for this sort key.  Note we're
-		 * underneath any outer joins, so nullable_relids should be NULL.
+		 * OK, try to make a canonical pathkey for this sort key.
 		 */
 		cpathkey = make_pathkey_from_sortinfo(root,
 											  indexkey,
-											  NULL,
 											  index->sortopfamily[i],
 											  index->opcintype[i],
 											  index->indexcollations[i],
@@ -743,14 +735,12 @@ build_partition_pathkeys(PlannerInfo *root, RelOptInfo *partrel,
 		/*
 		 * Try to make a canonical pathkey for this partkey.
 		 *
-		 * We're considering a baserel scan, so nullable_relids should be
-		 * NULL.  Also, we assume the PartitionDesc lists any NULL partition
-		 * last, so we treat the scan like a NULLS LAST index: we have
-		 * nulls_first for backwards scan only.
+		 * We assume the PartitionDesc lists any NULL partition last, so we
+		 * treat the scan like a NULLS LAST index: we have nulls_first for
+		 * backwards scan only.
 		 */
 		cpathkey = make_pathkey_from_sortinfo(root,
 											  keyCol,
-											  NULL,
 											  partscheme->partopfamily[i],
 											  partscheme->partopcintype[i],
 											  partscheme->partcollation[i],
@@ -799,7 +789,7 @@ build_partition_pathkeys(PlannerInfo *root, RelOptInfo *partrel,
  *	  Build a pathkeys list that describes an ordering by a single expression
  *	  using the given sort operator.
  *
- * expr, nullable_relids, and rel are as for make_pathkey_from_sortinfo.
+ * expr and rel are as for make_pathkey_from_sortinfo.
  * We induce the other arguments assuming default sort order for the operator.
  *
  * Similarly to make_pathkey_from_sortinfo, the result is NIL if create_it
@@ -808,7 +798,6 @@ build_partition_pathkeys(PlannerInfo *root, RelOptInfo *partrel,
 List *
 build_expression_pathkey(PlannerInfo *root,
 						 Expr *expr,
-						 Relids nullable_relids,
 						 Oid opno,
 						 Relids rel,
 						 bool create_it)
@@ -827,7 +816,6 @@ build_expression_pathkey(PlannerInfo *root,
 
 	cpathkey = make_pathkey_from_sortinfo(root,
 										  expr,
-										  nullable_relids,
 										  opfamily,
 										  opcintype,
 										  exprCollation((Node *) expr),
@@ -908,14 +896,11 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 				 * expression is *not* volatile in the outer query: it's just
 				 * a Var referencing whatever the subquery emitted. (IOW, the
 				 * outer query isn't going to re-execute the volatile
-				 * expression itself.)	So this is okay.  Likewise, it's
-				 * correct to pass nullable_relids = NULL, because we're
-				 * underneath any outer joins appearing in the outer query.
+				 * expression itself.)	So this is okay.
 				 */
 				outer_ec =
 					get_eclass_for_sort_expr(root,
 											 (Expr *) outer_var,
-											 NULL,
 											 sub_eclass->ec_opfamilies,
 											 sub_member->em_datatype,
 											 sub_eclass->ec_collation,
@@ -997,7 +982,6 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 					/* See if we have a matching EC for the TLE */
 					outer_ec = get_eclass_for_sort_expr(root,
 														(Expr *) outer_var,
-														NULL,
 														sub_eclass->ec_opfamilies,
 														sub_expr_type,
 														sub_expr_coll,
@@ -1138,13 +1122,6 @@ build_join_pathkeys(PlannerInfo *root,
  * The resulting PathKeys are always in canonical form.  (Actually, there
  * is no longer any code anywhere that creates non-canonical PathKeys.)
  *
- * We assume that root->nullable_baserels is the set of base relids that could
- * have gone to NULL below the SortGroupClause expressions.  This is okay if
- * the expressions came from the query's top level (ORDER BY, DISTINCT, etc)
- * and if this function is only invoked after deconstruct_jointree.  In the
- * future we might have to make callers pass in the appropriate
- * nullable-relids set, but for now it seems unnecessary.
- *
  * 'sortclauses' is a list of SortGroupClause nodes
  * 'tlist' is the targetlist to find the referenced tlist entries in
  */
@@ -1210,7 +1187,6 @@ make_pathkeys_for_sortclauses_extended(PlannerInfo *root,
 		}
 		pathkey = make_pathkey_from_sortop(root,
 										   sortkey,
-										   root->nullable_baserels,
 										   sortcl->sortop,
 										   sortcl->nulls_first,
 										   sortcl->tleSortGroupRef,
@@ -1268,7 +1244,6 @@ initialize_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
 	restrictinfo->left_ec =
 		get_eclass_for_sort_expr(root,
 								 (Expr *) get_leftop(clause),
-								 restrictinfo->nullable_relids,
 								 restrictinfo->mergeopfamilies,
 								 lefttype,
 								 ((OpExpr *) clause)->inputcollid,
@@ -1278,7 +1253,6 @@ initialize_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
 	restrictinfo->right_ec =
 		get_eclass_for_sort_expr(root,
 								 (Expr *) get_rightop(clause),
-								 restrictinfo->nullable_relids,
 								 restrictinfo->mergeopfamilies,
 								 righttype,
 								 ((OpExpr *) clause)->inputcollid,