Fix incorrect strictness test for ArrayCoerceExpr expressions.

The recursion in contain_nonstrict_functions_walker() was done wrong,
causing the strictness check to be bypassed for a parse node that
is the immediate input of an ArrayCoerceExpr node.  This could allow,
for example, incorrect decisions about whether a strict SQL function
can be inlined.

I didn't add a regression test, because (a) the bug is so narrow
and (b) I couldn't think of a test case that wasn't dependent on a
large number of other behaviors, to the point where it would likely
soon rot to the point of not testing what it was intended to.

I broke this in commit c12d570fa, so back-patch to v11.

Discussion: https://postgr.es/m/27571.1550617881@sss.pgh.pa.us

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 3737166e8f49965fddf87e7ca45bf4d49677e685..2d0bad7cde98a148631aa2e83179b523012c5970 100644 (file)
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -1179,9 +1179,8 @@ contain_nonstrict_functions_walker(Node *node, void *context)
                 * the per-element expression is; so we should ignore elemexpr and
                 * recurse only into the arg.
                 */
-               return expression_tree_walker((Node *) ((ArrayCoerceExpr *) node)->arg,
-                                                                         contain_nonstrict_functions_walker,
-                                                                         context);
+               return contain_nonstrict_functions_walker((Node *) ((ArrayCoerceExpr *) node)->arg,
+                                                                                                 context);
        }
        if (IsA(node, CaseExpr))
                return true;