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, 3 insertions, 0 deletions

diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 5fcf2741988..ef04c342a29 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -367,6 +367,7 @@ OffsetVarNodes_walker(Node *node, OffsetVarNodes_context *context)
 	/* Shouldn't need to handle other planner auxiliary nodes here */
 	Assert(!IsA(node, PlanRowMark));
 	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));
 
@@ -548,6 +549,7 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
 	}
 	/* Shouldn't need to handle other planner auxiliary nodes here */
 	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));
 
@@ -816,6 +818,7 @@ rangeTableEntry_used_walker(Node *node,
 	Assert(!IsA(node, PlaceHolderVar));
 	Assert(!IsA(node, PlanRowMark));
 	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, LateralJoinInfo));
 	Assert(!IsA(node, AppendRelInfo));
 	Assert(!IsA(node, PlaceHolderInfo));
 	Assert(!IsA(node, MinMaxAggInfo));