From 34f3b396a6554903007031b0541781b7ecdd6e4d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 11 Nov 2012 19:56:10 -0500
Subject: [PATCH] Check for stack overflow in transformSetOperationTree().

Since transformSetOperationTree() recurses, it can be driven to stack
overflow with enough UNION/INTERSECT/EXCEPT clauses in a query.  Add a
check to ensure it fails cleanly instead of crashing.  Per report from
Matthew Gerber (though it's not clear whether this is the only thing
going wrong for him).

Historical note: I think the reasoning behind not putting a check here in
the beginning was that the check in transformExpr() ought to be sufficient
to guard the whole parser.  However, because transformSetOperationTree()
recurses all the way to the bottom of the set-operation tree before doing
any analysis of the statement's expressions, that check doesn't save it.
---
 src/backend/parser/analyze.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 823d3b445a7..7085035c525 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -26,6 +26,7 @@
 
 #include "access/sysattr.h"
 #include "catalog/pg_type.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/var.h"
@@ -1487,6 +1488,9 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt,
 
 	Assert(stmt && IsA(stmt, SelectStmt));
 
+	/* Guard against stack overflow due to overly complex set-expressions */
+	check_stack_depth();
+
 	/*
 	 * Validity-check both leaf and internal SELECTs for disallowed ops.
 	 */
-- 
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