Make some small planner API cleanups.

Move a few very simple node-creation and node-type-testing functions
from the planner's clauses.c to nodes/makefuncs and nodes/nodeFuncs.
There's nothing planner-specific about them, as evidenced by the
number of other places that were using them.

While at it, rename and_clause() etc to is_andclause() etc, to clarify
that they are node-type-testing functions not node-creation functions.
And use "static inline" implementations for the shortest ones.

Also, modify flatten_join_alias_vars() and some subsidiary functions
to take a Query not a PlannerInfo to define the join structure that
Vars should be translated according to.  They were only using the
"parse" field of the PlannerInfo anyway, so this just requires removing
one level of indirection.  The advantage is that now parse_agg.c can
use flatten_join_alias_vars() without the horrid kluge of creating an
incomplete PlannerInfo, which will allow that file to be decoupled from
relation.h in a subsequent patch.

Discussion: https://postgr.es/m/11460.1548706639@sss.pgh.pa.us

1 files changed, 72 insertions, 0 deletions

diff --git a/src/include/nodes/nodeFuncs.h b/src/include/nodes/nodeFuncs.h
index a9f76bbb330..98759346d12 100644
--- a/src/include/nodes/nodeFuncs.h
+++ b/src/include/nodes/nodeFuncs.h
@@ -50,6 +50,78 @@ extern void fix_opfuncids(Node *node);
 extern void set_opfuncid(OpExpr *opexpr);
 extern void set_sa_opfuncid(ScalarArrayOpExpr *opexpr);
 
+/* Is clause a FuncExpr clause? */
+static inline bool
+is_funcclause(const void *clause)
+{
+	return clause != NULL && IsA(clause, FuncExpr);
+}
+
+/* Is clause an OpExpr clause? */
+static inline bool
+is_opclause(const void *clause)
+{
+	return clause != NULL && IsA(clause, OpExpr);
+}
+
+/* Extract left arg of a binary opclause, or only arg of a unary opclause */
+static inline Node *
+get_leftop(const void *clause)
+{
+	const OpExpr *expr = (const OpExpr *) clause;
+
+	if (expr->args != NIL)
+		return (Node *) linitial(expr->args);
+	else
+		return NULL;
+}
+
+/* Extract right arg of a binary opclause (NULL if it's a unary opclause) */
+static inline Node *
+get_rightop(const void *clause)
+{
+	const OpExpr *expr = (const OpExpr *) clause;
+
+	if (list_length(expr->args) >= 2)
+		return (Node *) lsecond(expr->args);
+	else
+		return NULL;
+}
+
+/* Is clause an AND clause? */
+static inline bool
+is_andclause(const void *clause)
+{
+	return (clause != NULL &&
+			IsA(clause, BoolExpr) &&
+			((const BoolExpr *) clause)->boolop == AND_EXPR);
+}
+
+/* Is clause an OR clause? */
+static inline bool
+is_orclause(const void *clause)
+{
+	return (clause != NULL &&
+			IsA(clause, BoolExpr) &&
+			((const BoolExpr *) clause)->boolop == OR_EXPR);
+}
+
+/* Is clause a NOT clause? */
+static inline bool
+is_notclause(const void *clause)
+{
+	return (clause != NULL &&
+			IsA(clause, BoolExpr) &&
+			((const BoolExpr *) clause)->boolop == NOT_EXPR);
+}
+
+/* Extract argument from a clause known to be a NOT clause */
+static inline Expr *
+get_notclausearg(const void *notclause)
+{
+	return (Expr *) linitial(((const BoolExpr *) notclause)->args);
+}
+
 extern bool check_functions_in_node(Node *node, check_function_callback checker,
 						void *context);