expression: push down EXTRACT to TiFlash (pingcap#22832)

expression/expr_to_pb_test.go

@@ -629,6 +629,11 @@ func (s *testEvaluatorSuite) TestExprPushDownToFlash(c *C) {
 	c.Assert(err, IsNil)
 	exprs = append(exprs, function)
 
+	// ExtractDatetime: can be pushed
+	function, err = NewFunction(mock.NewContext(), ast.Extract, types.NewFieldType(mysql.TypeLonglong), stringColumn, datetimeColumn)
+	c.Assert(err, IsNil)
+	exprs = append(exprs, function)
+
 	// CastIntAsInt
 	function, err = NewFunction(mock.NewContext(), ast.Cast, types.NewFieldType(mysql.TypeLonglong), intColumn)
 	c.Assert(err, IsNil)
@@ -726,9 +731,15 @@ func (s *testEvaluatorSuite) TestExprPushDownToFlash(c *C) {
 	function, err = NewFunction(mock.NewContext(), ast.JSONDepth, types.NewFieldType(mysql.TypeLonglong), jsonColumn)
 	c.Assert(err, IsNil)
 	exprs = append(exprs, function)
+
+	// ExtractDatetimeFromString: can not be pushed
+	function, err = NewFunction(mock.NewContext(), ast.Extract, types.NewFieldType(mysql.TypeLonglong), stringColumn, stringColumn)
+	c.Assert(err, IsNil)
+	exprs = append(exprs, function)
+
 	pushed, remained := PushDownExprs(sc, exprs, client, kv.TiFlash)
-	c.Assert(len(pushed), Equals, len(exprs)-1)
-	c.Assert(len(remained), Equals, 1)
+	c.Assert(len(pushed), Equals, len(exprs)-2)
+	c.Assert(len(remained), Equals, 2)
 }
 
 func (s *testEvaluatorSuite) TestExprOnlyPushDownToFlash(c *C) {

expression/expression.go

@@ -1044,6 +1044,7 @@ func canFuncBePushed(sf *ScalarFunction, storeType kv.StoreType) bool {
 		ast.DateAdd,
 		ast.FromUnixTime,
 		ast.UnixTimestamp,
+		ast.Extract,
 
 		// encryption functions.
 		ast.MD5,
@@ -1059,8 +1060,9 @@ func canFuncBePushed(sf *ScalarFunction, storeType kv.StoreType) bool {
 		ast.Inet6Aton,
 		ast.IsIPv4,
 		ast.IsIPv4Compat,
-		ast.IsIPv4Mapped,leiyu
-		ast.IsIPv6:
+		ast.IsIPv4Mapped,
+		ast.IsIPv6,
+		ast.UUID:
 		ret = true
 
 	// A special case: Only push down Round by signature
@@ -1206,7 +1208,7 @@ func CanExprsPushDown(sc *stmtctx.StatementContext, exprs []Expression, client k
 func scalarExprSupportedByTiKV(function *ScalarFunction) bool {
 	switch function.FuncName.L {
 	case ast.Substr, ast.Substring, ast.DateAdd, ast.TimestampDiff, ast.DateDiff, ast.UnixTimestamp,
-		ast.FromUnixTime:
+		ast.FromUnixTime, ast.Extract:
 		return false
 	default:
 		return true
@@ -1262,6 +1264,13 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		default:
 			return false
 		}
+	case ast.Extract:
+		switch function.Function.PbCode() {
+		case tipb.ScalarFuncSig_ExtractDatetime:
+			return true
+		default:
+			return false
+		}
 	default:
 		return false
 	}