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commit    1f91c8ca1d2edc66c688ee719eded79ecd0e8f1b
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Oct 03 17:37:53 2012 +0000
First released in: 9.3.0, 9.2.2

    Avoid planner crash/Assert failure with joins to unflattened subqueries.
    
    examine_simple_variable supposed that any RTE_SUBQUERY rel it gets pointed
    at must have been planned already.  However, this isn't a safe assumption
    because we must do selectivity estimation while generating indexscan paths,
    and that code might look at join clauses involving a rel that the loop in
    set_base_rel_sizes() hasn't reached yet.  The simplest fix is to play dumb
    in such a situation, that is give up trying to extract any stats for the
    Var.  This could possibly be improved by making a separate pass over the
    RTE list to plan each unflattened subquery before we start the main
    planning work --- but that would be pretty invasive and it doesn't seem
    worth it, for now at least.  (We couldn't just break set_base_rel_sizes()
    into two loops: the prescan would need to handle all subquery rels in the
    query, not only those in the current join subproblem.)
    
    This bug was introduced in commit 1cb108efb0e60d87e4adec38e7636b6e8efbeb57,
    although I think that subsequent changes may have exposed it more than it
    was originally.  Per bug #7580 from Maxim Boguk.


 src/backend/utils/adt/selfuncs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 2ab26dea290..61100aec4ae 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4518,8 +4518,10 @@ examine_simple_variable(PlannerInfo *root, Var *var,
 		 */
 		rel = find_base_rel(root, var->varno);
 
-		/* Subquery should have been planned already */
-		Assert(rel->subroot && IsA(rel->subroot, PlannerInfo));
+		/* If the subquery hasn't been planned yet, we have to punt */
+		if (rel->subroot == NULL)
+			return;
+		Assert(IsA(rel->subroot, PlannerInfo));
 
 		/*
 		 * Switch our attention to the subquery as mangled by the planner. It


[parent: fe3b5eb08a16]