On 2017/10/23 2:07, Tom Lane wrote:
> Andreas Seltenreich <[email protected]> writes:
>> testing master as of 7c981590c2, sqlsmith just triggered the following
>> assertion:
>> TRAP: FailedAssertion("!(!((((const Node*)(node))->type) == T_SubLink))",
>> File: "prepunion.c", Line: 2231)
>
> Hmm. adjust_appendrel_attrs() thinks it's only used after conversion
> of sublinks to subplans, but this is a counterexample. I wonder if
> that assumption was ever correct? Or maybe we need to rethink what
> it does when recursing into RTE subqueries.
Looking at the backtrace, the crashing SubLink seems to have been
referenced from a PlaceHolderVar that is in turn referenced by
joinaliasvars of a JOIN rte in query->rtable.
I wonder if we shouldn't just ignore those (joinaliasvars in JOIN rtes)
while adjust_appendrel_attrs() is doing its job on a Query, just like we
ask to ignore subqueries by passing QTW_IGNORE_RC_SUBQUERIES to
query_tree_mutator()? IOW, it doesn't look like anything critically
depends on the Vars referenced from joinaliasvars being translated at that
point in inheritance_planner(), but I may be missing something.
The attached patch to do the same, while didn't break any existing tests,
fixed the crash reported by OP.
Thoughts?
Thanks,
Amit
diff --git a/src/backend/optimizer/prep/prepunion.c
b/src/backend/optimizer/prep/prepunion.c
index 1c84a2cb28..4bdfe73d29 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -1964,7 +1964,8 @@ adjust_appendrel_attrs(PlannerInfo *root, Node *node, int
nappinfos,
newnode = query_tree_mutator((Query *) node,
adjust_appendrel_attrs_mutator,
(void
*) &context,
-
QTW_IGNORE_RC_SUBQUERIES);
+
QTW_IGNORE_RC_SUBQUERIES |
+
QTW_IGNORE_JOINALIASES);
for (cnt = 0; cnt < nappinfos; cnt++)
{
AppendRelInfo *appinfo = appinfos[cnt];
--
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