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.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/backend/optimizer/path/tidpath.c b/src/backend/optimizer/path/tidpath.c
index 35702c27050..36390d50a2e 100644
--- a/src/backend/optimizer/path/tidpath.c
+++ b/src/backend/optimizer/path/tidpath.c
@@ -249,10 +249,20 @@ TidQualFromRestrictinfo(List *restrictinfo, int varno)
 void
 create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel)
 {
+	Relids		required_outer;
 	List	   *tidquals;
 
+	/*
+	 * We don't support pushing join clauses into the quals of a tidscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.  (That can only happen if the tidscan is on a relation
+	 * pulled up out of a UNION ALL appendrel.)
+	 */
+	required_outer = rel->lateral_relids;
+
 	tidquals = TidQualFromRestrictinfo(rel->baserestrictinfo, rel->relid);
 
 	if (tidquals)
-		add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals));
+		add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals,
+												   required_outer));
 }