Implement SQL-standard LATERAL subqueries.

This patch implements the standard syntax of LATERAL attached to a
sub-SELECT in FROM, and also allows LATERAL attached to a function in FROM,
since set-returning function calls are expected to be one of the principal
use-cases.

The main change here is a rewrite of the mechanism for keeping track of
which relations are visible for column references while the FROM clause is
being scanned.  The parser "namespace" lists are no longer lists of bare
RTEs, but are lists of ParseNamespaceItem structs, which carry an RTE
pointer as well as some visibility-controlling flags.  Aside from
supporting LATERAL correctly, this lets us get rid of the ancient hacks
that required rechecking subqueries and JOIN/ON and function-in-FROM
expressions for invalid references after they were initially parsed.
Invalid column references are now always correctly detected on sight.

In passing, remove assorted parser error checks that are now dead code by
virtue of our having gotten rid of add_missing_from, as well as some
comments that are obsolete for the same reason.  (It was mainly
add_missing_from that caused so much fudging here in the first place.)

The planner support for this feature is very minimal, and will be improved
in future patches.  It works well enough for testing purposes, though.

catversion bump forced due to new field in RangeTblEntry.

3 files changed, 5 insertions, 3 deletions

diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index b2cdb3d62e9..e3d33d69ba3 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -81,7 +81,7 @@ extern void cost_tidscan(Path *path, PlannerInfo *root,
 extern void cost_subqueryscan(Path *path, PlannerInfo *root,
 				  RelOptInfo *baserel, ParamPathInfo *param_info);
 extern void cost_functionscan(Path *path, PlannerInfo *root,
-				  RelOptInfo *baserel);
+				  RelOptInfo *baserel, ParamPathInfo *param_info);
 extern void cost_valuesscan(Path *path, PlannerInfo *root,
 				RelOptInfo *baserel);
 extern void cost_ctescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 385bae6eb80..3af1172cbe5 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -69,7 +69,8 @@ extern UniquePath *create_unique_path(PlannerInfo *root, RelOptInfo *rel,
 				   Path *subpath, SpecialJoinInfo *sjinfo);
 extern Path *create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel,
 						 List *pathkeys, Relids required_outer);
-extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel);
+extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
+						 Relids required_outer);
 extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
 extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
 extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
diff --git a/src/include/optimizer/var.h b/src/include/optimizer/var.h
index f546362b680..ec21df3a7e0 100644
--- a/src/include/optimizer/var.h
+++ b/src/include/optimizer/var.h
@@ -31,11 +31,12 @@ typedef enum
 } PVCPlaceHolderBehavior;
 
 extern Relids pull_varnos(Node *node);
+extern Relids pull_varnos_of_level(Node *node, int levelsup);
 extern void pull_varattnos(Node *node, Index varno, Bitmapset **varattnos);
+extern List *pull_vars_of_level(Node *node, int levelsup);
 extern bool contain_var_clause(Node *node);
 extern bool contain_vars_of_level(Node *node, int levelsup);
 extern int	locate_var_of_level(Node *node, int levelsup);
-extern int	locate_var_of_relation(Node *node, int relid, int levelsup);
 extern int	find_minimum_var_level(Node *node);
 extern List *pull_var_clause(Node *node, PVCAggregateBehavior aggbehavior,
 				PVCPlaceHolderBehavior phbehavior);