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, 2 insertions, 1 deletions

diff --git a/src/backend/optimizer/plan/planagg.c b/src/backend/optimizer/plan/planagg.c
index 0bbca071fb0..373f65b76fe 100644
--- a/src/backend/optimizer/plan/planagg.c
+++ b/src/backend/optimizer/plan/planagg.c
@@ -392,8 +392,9 @@ build_minmax_path(PlannerInfo *root, MinMaxAggInfo *mminfo,
 	subroot->parse = parse = (Query *) copyObject(root->parse);
 	/* make sure subroot planning won't change root->init_plans contents */
 	subroot->init_plans = list_copy(root->init_plans);
-	/* There shouldn't be any OJ info to translate, as yet */
+	/* There shouldn't be any OJ or LATERAL info to translate, as yet */
 	Assert(subroot->join_info_list == NIL);
+	Assert(subroot->lateral_info_list == NIL);
 	/* and we haven't created PlaceHolderInfos, either */
 	Assert(subroot->placeholder_list == NIL);