Extend DomainHasConstraints() to optionally check constraint volatility

Add an optional bool *has_volatile output parameter to
DomainHasConstraints().  When non-NULL, the function checks whether any
CHECK constraint contains a volatile expression.  Callers that don't
need this information pass NULL and get the same behavior as before.

This is needed by a subsequent commit that enables the fast default
optimization for domains with non-volatile constraints: we can safely
evaluate such constraints once at ALTER TABLE time, but volatile
constraints require a full table rewrite.

Author: Jian He <jian.universality@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Reviewed-by: Viktor Holmberg <viktor.holmberg@aiven.io>
Discussion: https://postgr.es/m/CACJufxE_+iZBR1i49k_AHigppPwLTJi6km8NOsC7FWvKdEmmXg@mail.gmail.com

src/backend/commands/copyfrom.c

@@ -1653,7 +1653,7 @@ BeginCopyFrom(ParseState *pstate,
 
 			Form_pg_attribute att = TupleDescAttr(tupDesc, attno - 1);
 
-			cstate->domain_with_constraint[i] = DomainHasConstraints(att->atttypid);
+			cstate->domain_with_constraint[i] = DomainHasConstraints(att->atttypid, NULL);
 		}
 	}
 

src/backend/commands/tablecmds.c

@@ -7531,7 +7531,7 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			defval = (Expr *) build_column_default(rel, attribute->attnum);
 
 		/* Build CoerceToDomain(NULL) expression if needed */
-		has_domain_constraints = DomainHasConstraints(attribute->atttypid);
+		has_domain_constraints = DomainHasConstraints(attribute->atttypid, NULL);
 		if (!defval && has_domain_constraints)
 		{
 			Oid			baseTypeId;
@@ -14893,7 +14893,7 @@ ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno)
 		{
 			CoerceToDomain *d = (CoerceToDomain *) expr;
 
-			if (DomainHasConstraints(d->resulttype))
+			if (DomainHasConstraints(d->resulttype, NULL))
 				return true;
 			expr = (Node *) d->arg;
 		}

src/backend/executor/execExpr.c

@@ -5061,6 +5061,6 @@ ExecInitJsonCoercion(ExprState *state, JsonReturning *returning,
 	scratch.d.jsonexpr_coercion.exists_cast_to_int = exists_coerce &&
 		getBaseType(returning->typid) == INT4OID;
 	scratch.d.jsonexpr_coercion.exists_check_domain = exists_coerce &&
-		DomainHasConstraints(returning->typid);
+		DomainHasConstraints(returning->typid, NULL);
 	ExprEvalPushStep(state, &scratch);
 }

src/backend/optimizer/util/clauses.c

@@ -4039,7 +4039,7 @@ eval_const_expressions_mutator(Node *node,
 				arg = eval_const_expressions_mutator((Node *) cdomain->arg,
 													 context);
 				if (context->estimate ||
-					!DomainHasConstraints(cdomain->resulttype))
+					!DomainHasConstraints(cdomain->resulttype, NULL))
 				{
 					/* Record dependency, if this isn't estimation mode */
 					if (context->root && !context->estimate)

src/backend/parser/parse_expr.c

@@ -4628,7 +4628,7 @@ transformJsonFuncExpr(ParseState *pstate, JsonFuncExpr *func)
 			if (jsexpr->returning->typid != TEXTOID)
 			{
 				if (get_typtype(jsexpr->returning->typid) == TYPTYPE_DOMAIN &&
-					DomainHasConstraints(jsexpr->returning->typid))
+					DomainHasConstraints(jsexpr->returning->typid, NULL))
 					jsexpr->use_json_coercion = true;
 				else
 					jsexpr->use_io_coercion = true;

src/backend/utils/cache/typcache.c

@@ -1485,10 +1485,14 @@ UpdateDomainConstraintRef(DomainConstraintRef *ref)
 /*
  * DomainHasConstraints --- utility routine to check if a domain has constraints
  *
+ * Returns true if the domain has any constraints at all.  If has_volatile
+ * is not NULL, also checks whether any CHECK constraint contains a volatile
+ * expression and sets *has_volatile accordingly.
+ *
  * This is defined to return false, not fail, if type is not a domain.
  */
 bool
-DomainHasConstraints(Oid type_id)
+DomainHasConstraints(Oid type_id, bool *has_volatile)
 {
 	TypeCacheEntry *typentry;
 
@@ -1498,7 +1502,26 @@ DomainHasConstraints(Oid type_id)
 	 */
 	typentry = lookup_type_cache(type_id, TYPECACHE_DOMAIN_CONSTR_INFO);
 
-	return (typentry->domainData != NULL);
+	if (typentry->domainData == NULL)
+		return false;
+
+	if (has_volatile)
+	{
+		*has_volatile = false;
+
+		foreach_node(DomainConstraintState, constrstate,
+					 typentry->domainData->constraints)
+		{
+			if (constrstate->constrainttype == DOM_CONSTRAINT_CHECK &&
+				contain_volatile_functions((Node *) constrstate->check_expr))
+			{
+				*has_volatile = true;
+				break;
+			}
+		}
+	}
+
+	return true;
 }
 
 

src/include/utils/typcache.h

@@ -183,7 +183,7 @@ extern void InitDomainConstraintRef(Oid type_id, DomainConstraintRef *ref,
 
 extern void UpdateDomainConstraintRef(DomainConstraintRef *ref);
 
-extern bool DomainHasConstraints(Oid type_id);
+extern bool DomainHasConstraints(Oid type_id, bool *has_volatile);
 
 extern TupleDesc lookup_rowtype_tupdesc(Oid type_id, int32 typmod);