Fix assorted missing infrastructure for ON CONFLICT.

subquery_planner() failed to apply expression preprocessing to the
arbiterElems and arbiterWhere fields of an OnConflictExpr.  No doubt the
theory was that this wasn't necessary because we don't actually try to
execute those expressions; but that's wrong, because it results in failure
to match to index expressions or index predicates that are changed at all
by preprocessing.  Per bug #14132 from Reynold Smith.

Also add pullup_replace_vars processing for onConflictWhere.  Perhaps
it's impossible to have a subquery reference there, but I'm not exactly
convinced; and even if true today it's a failure waiting to happen.

Also add some comments to other places where one or another field of
OnConflictExpr is intentionally ignored, with explanation as to why it's
okay to do so.

Also, catalog/dependency.c failed to record any dependency on the named
constraint in ON CONFLICT ON CONSTRAINT, allowing such a constraint to
be dropped while rules exist that depend on it, and allowing pg_dump to
dump such a rule before the constraint it refers to.  The normal execution
path managed to error out reasonably for a dangling constraint reference,
but ruleutils.c dumped core; so in addition to fixing the omission, add
a protective check in ruleutils.c, since we can't retroactively add a
dependency in existing databases.

Back-patch to 9.5 where this code was introduced.

Report: <20160510190350.2608.48667@wrigleys.postgresql.org>

1 files changed, 14 insertions, 3 deletions

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 6770836dc89..75d93c08db2 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -77,6 +77,7 @@ create_upper_paths_hook_type create_upper_paths_hook = NULL;
 #define EXPRKIND_APPINFO		7
 #define EXPRKIND_PHV			8
 #define EXPRKIND_TABLESAMPLE	9
+#define EXPRKIND_ARBITER_ELEM	10
 
 /* Passthrough data for standard_qp_callback */
 typedef struct
@@ -620,13 +621,23 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 
 	if (parse->onConflict)
 	{
+		parse->onConflict->arbiterElems = (List *)
+			preprocess_expression(root,
+								  (Node *) parse->onConflict->arbiterElems,
+								  EXPRKIND_ARBITER_ELEM);
+		parse->onConflict->arbiterWhere =
+			preprocess_expression(root,
+								  parse->onConflict->arbiterWhere,
+								  EXPRKIND_QUAL);
 		parse->onConflict->onConflictSet = (List *)
-			preprocess_expression(root, (Node *) parse->onConflict->onConflictSet,
+			preprocess_expression(root,
+								  (Node *) parse->onConflict->onConflictSet,
 								  EXPRKIND_TARGET);
-
 		parse->onConflict->onConflictWhere =
-			preprocess_expression(root, (Node *) parse->onConflict->onConflictWhere,
+			preprocess_expression(root,
+								  parse->onConflict->onConflictWhere,
 								  EXPRKIND_QUAL);
+		/* exclRelTlist contains only Vars, so no preprocessing needed */
 	}
 
 	root->append_rel_list = (List *)