add function DomainHaveVolatileConstraints

the signature is:
extern bool DomainHaveVolatileConstraints(Oid type_id, bool *have_volatile);

Returns true if the Domain has any constraints.  If you want check this domain
have any volatile check constraints, make sure have_volatile is not NULL.

discussion: https://postgr.es/m/CACJufxE_+iZBR1i49k_AHigppPwLTJi6km8NOsC7FWvKdEmmXg@mail.gmail.com

Author: jianhe-fun

src/backend/utils/cache/typcache.c

@@ -1500,6 +1500,46 @@ DomainHasConstraints(Oid type_id)
 }
 
 
+/*
+ * Check whether a domain has any constraints, and determine if any of those
+ * constraints contain volatile expressions.
+ *
+ * To detect volatile expressions within domain check constraints, ensure that
+ * have_volatile is not NULL. If have_volatile is NULL, the behavior is
+ * equivalent to that of DomainHasConstraints.
+ */
+bool
+DomainHaveVolatileConstraints(Oid type_id, bool *have_volatile)
+{
+	TypeCacheEntry *typentry;
+
+	/*
+	 * Note: a side effect is to cause the typcache's domain data to become
+	 * valid.  This is fine since we'll likely need it soon if there is any.
+	 */
+	typentry = lookup_type_cache(type_id, TYPECACHE_DOMAIN_CONSTR_INFO);
+
+	if (typentry->domainData != NULL)
+	{
+		ListCell   *lc;
+
+		foreach(lc, typentry->domainData->constraints)
+		{
+			DomainConstraintState *r = (DomainConstraintState *) lfirst(lc);
+
+			if (r->constrainttype == DOM_CONSTRAINT_CHECK &&
+				contain_volatile_functions((Node *) r->check_expr))
+			{
+				if (have_volatile)
+					*have_volatile = true;
+				break;
+			}
+		}
+		return true;
+	}
+	return false;
+}
+
 /*
  * array_element_has_equality and friends are helper routines to check
  * whether we should believe that array_eq and related functions will work

src/include/utils/typcache.h

@@ -184,6 +184,7 @@ extern void InitDomainConstraintRef(Oid type_id, DomainConstraintRef *ref,
 extern void UpdateDomainConstraintRef(DomainConstraintRef *ref);
 
 extern bool DomainHasConstraints(Oid type_id);
+extern bool DomainHaveVolatileConstraints(Oid type_id, bool *have_volatile);
 
 extern TupleDesc lookup_rowtype_tupdesc(Oid type_id, int32 typmod);