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.

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 114454951d122d7b6c96ac8c98ae645323d0830e..973639b48fac4f7ec5f08efd0750aa8ea97d0a97 100644 (file)
--- 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"
@@ -1520,6 +1521,9 @@ 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.
         */