Refactor to reduce code duplication for function property checking.

As noted by Andres Freund, we'd accumulated quite a few similar functions
in clauses.c that examine all functions in an expression tree to see if
they satisfy some boolean test.  Reduce the duplication by inventing a
function check_functions_in_node() that applies a simple callback function
to each SQL function OID appearing in a given expression node.  This also
fixes some arguable oversights; for example, contain_mutable_functions()
did not check aggregate or window functions for mutability.  I doubt that
that represents a live bug at the moment, because we don't really consider
mutability for aggregates; but it might someday be one.

I chose to put check_functions_in_node() in nodeFuncs.c because it seemed
like other modules might wish to use it in future.  That in turn forced
moving set_opfuncid() et al into nodeFuncs.c, as the alternative was for
nodeFuncs.c to depend on optimizer/setrefs.c which didn't seem very clean.

In passing, teach contain_leaked_vars_walker() about a few more expression
node types it can safely look through, and improve the rather messy and
undercommented code in has_parallel_hazard_walker().

Discussion: <20160527185853.ziol2os2zskahl7v@alap3.anarazel.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index 1dacc996e80..97af1429296 100644
--- a/src/include/nodes/nodeFuncs.h
+++ b/src/include/nodes/nodeFuncs.h
@@ -25,6 +25,9 @@
 #define QTW_EXAMINE_RTES			0x10		/* examine RTEs */
 #define QTW_DONT_COPY_QUERY			0x20		/* do not copy top Query */
 
+/* callback function for check_functions_in_node */
+typedef bool (*check_function_callback) (Oid func_id, void *context);
+
 
 extern Oid	exprType(const Node *expr);
 extern int32 exprTypmod(const Node *expr);
@@ -40,6 +43,13 @@ extern void exprSetInputCollation(Node *expr, Oid inputcollation);
 
 extern int	exprLocation(const Node *expr);
 
+extern void fix_opfuncids(Node *node);
+extern void set_opfuncid(OpExpr *opexpr);
+extern void set_sa_opfuncid(ScalarArrayOpExpr *opexpr);
+
+extern bool check_functions_in_node(Node *node, check_function_callback checker,
+						void *context);
+
 extern bool expression_tree_walker(Node *node, bool (*walker) (),
 											   void *context);
 extern Node *expression_tree_mutator(Node *node, Node *(*mutator) (),