Fix up planner infrastructure to support LATERAL properly.

This patch takes care of a number of problems having to do with failure
to choose valid join orders and incorrect handling of lateral references
pulled up from subqueries.  Notable changes:

* Add a LateralJoinInfo data structure similar to SpecialJoinInfo, to
represent join ordering constraints created by lateral references.
(I first considered extending the SpecialJoinInfo structure, but the
semantics are different enough that a separate data structure seems
better.)  Extend join_is_legal() and related functions to prevent trying
to form unworkable joins, and to ensure that we will consider joins that
satisfy lateral references even if the joins would be clauseless.

* Fill in the infrastructure needed for the last few types of relation scan
paths to support parameterization.  We'd have wanted this eventually
anyway, but it is necessary now because a relation that gets pulled up out
of a UNION ALL subquery may acquire a reltargetlist containing lateral
references, meaning that its paths *have* to be parameterized whether or
not we have any code that can push join quals down into the scan.

* Compute data about lateral references early in query_planner(), and save
in RelOptInfo nodes, to avoid repetitive calculations later.

* Assorted corner-case bug fixes.

There's probably still some bugs left, but this is a lot closer to being
real than it was before.

src/include/optimizer/cost.h

@@ -77,14 +77,15 @@ extern void cost_bitmap_and_node(BitmapAndPath *path, PlannerInfo *root);
 extern void cost_bitmap_or_node(BitmapOrPath *path, PlannerInfo *root);
 extern void cost_bitmap_tree_node(Path *path, Cost *cost, Selectivity *selec);
 extern void cost_tidscan(Path *path, PlannerInfo *root,
-			 RelOptInfo *baserel, List *tidquals);
+			 RelOptInfo *baserel, List *tidquals, ParamPathInfo *param_info);
 extern void cost_subqueryscan(Path *path, PlannerInfo *root,
 				  RelOptInfo *baserel, ParamPathInfo *param_info);
 extern void cost_functionscan(Path *path, PlannerInfo *root,
 				  RelOptInfo *baserel, ParamPathInfo *param_info);
 extern void cost_valuesscan(Path *path, PlannerInfo *root,
 				RelOptInfo *baserel, ParamPathInfo *param_info);
-extern void cost_ctescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
+extern void cost_ctescan(Path *path, PlannerInfo *root,
+			 RelOptInfo *baserel, ParamPathInfo *param_info);
 extern void cost_recursive_union(Plan *runion, Plan *nrterm, Plan *rterm);
 extern void cost_sort(Path *path, PlannerInfo *root,
 		  List *pathkeys, Cost input_cost, double tuples, int width,

src/include/optimizer/pathnode.h

@@ -55,7 +55,7 @@ extern BitmapOrPath *create_bitmap_or_path(PlannerInfo *root,
 					  RelOptInfo *rel,
 					  List *bitmapquals);
 extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
-					List *tidquals);
+					List *tidquals, Relids required_outer);
 extern AppendPath *create_append_path(RelOptInfo *rel, List *subpaths,
 				   Relids required_outer);
 extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
@@ -73,8 +73,10 @@ extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
 						 Relids required_outer);
 extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel,
 					   Relids required_outer);
-extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
-extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
+extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel,
+					Relids required_outer);
+extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel,
+						  Relids required_outer);
 extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
 						double rows, Cost startup_cost, Cost total_cost,
 						List *pathkeys,

src/include/optimizer/planmain.h

@@ -94,6 +94,8 @@ extern void add_base_rels_to_query(PlannerInfo *root, Node *jtnode);
 extern void build_base_rel_tlists(PlannerInfo *root, List *final_tlist);
 extern void add_vars_to_targetlist(PlannerInfo *root, List *vars,
 					   Relids where_needed, bool create_new_ph);
+extern void find_lateral_references(PlannerInfo *root);
+extern void create_lateral_join_info(PlannerInfo *root);
 extern List *deconstruct_jointree(PlannerInfo *root);
 extern void distribute_restrictinfo_to_rels(PlannerInfo *root,
 								RestrictInfo *restrictinfo);

src/include/optimizer/planner.h

@@ -42,6 +42,8 @@ extern bool is_dummy_plan(Plan *plan);
 
 extern Expr *expression_planner(Expr *expr);
 
+extern Expr *preprocess_phv_expression(PlannerInfo *root, Expr *expr);
+
 extern bool plan_cluster_use_sort(Oid tableOid, Oid indexOid);
 
 #endif   /* PLANNER_H */