expression: open CAST push down switcher default (pingcap#12652)

Signed-off-by: Lonng <heng@lonng.org>

cmd/explaintest/r/explain_easy.result

@@ -466,10 +466,10 @@ insert tb values ('1');
 explain select * from ta where a = 1;
 id	count	task	operator info
 Projection_5	8000.00	root	Column#1
-└─Selection_6	8000.00	root	eq(cast(Column#1), 1)
-  └─UnionScan_7	10000.00	root	eq(cast(Column#1), 1)
-    └─TableReader_9	10000.00	root	data:TableScan_8
-      └─TableScan_8	10000.00	cop[tikv]	table:ta, range:[-inf,+inf], keep order:false, stats:pseudo
+└─UnionScan_6	8000.00	root	eq(cast(Column#1), 1)
+  └─TableReader_9	8000.00	root	data:Selection_8
+    └─Selection_8	8000.00	cop[tikv]	eq(cast(Column#1), 1)
+      └─TableScan_7	10000.00	cop[tikv]	table:ta, range:[-inf,+inf], keep order:false, stats:pseudo
 rollback;
 drop table if exists t1, t2;
 create table t1(a int, b int, c int, primary key(a, b));

expression/aggregation/aggregation.go

@@ -153,7 +153,7 @@ func (af *aggFunction) updateSum(sc *stmtctx.StatementContext, evalCtx *AggEvalu
 			return nil
 		}
 	}
-	evalCtx.Value, err = calculateSum(sc, evalCtx.Value, value)
+	evalCtx.Value, err = calculateSum(sc, evalCtx.Value, value, a.GetType())
 	if err != nil {
 		return err
 	}

expression/aggregation/avg.go

@@ -35,7 +35,7 @@ func (af *avgFunction) updateAvg(sc *stmtctx.StatementContext, evalCtx *AggEvalu
 	if value.IsNull() {
 		return nil
 	}
-	evalCtx.Value, err = calculateSum(sc, evalCtx.Value, value)
+	evalCtx.Value, err = calculateSum(sc, evalCtx.Value, value, a.GetType())
 	if err != nil {
 		return err
 	}

expression/aggregation/util.go

@@ -15,6 +15,7 @@ package aggregation
 
 import (
 	"github.com/pingcap/errors"
+	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/codec"
@@ -54,7 +55,7 @@ func (d *distinctChecker) Check(values []types.Datum) (bool, error) {
 }
 
 // calculateSum adds v to sum.
-func calculateSum(sc *stmtctx.StatementContext, sum, v types.Datum) (data types.Datum, err error) {
+func calculateSum(sc *stmtctx.StatementContext, sum, v types.Datum, retType *types.FieldType) (data types.Datum, err error) {
 	// for avg and sum calculation
 	// avg and sum use decimal for integer and decimal type, use float for others
 	// see https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html
@@ -68,7 +69,22 @@ func calculateSum(sc *stmtctx.StatementContext, sum, v types.Datum) (data types.
 			data = types.NewDecimalDatum(d)
 		}
 	case types.KindMysqlDecimal:
-		data = types.CloneDatum(v)
+		dec := v.GetMysqlDecimal()
+		frac := retType.Decimal
+		if frac == types.UnspecifiedLength {
+			frac = mysql.MaxDecimalScale
+		}
+		if int(dec.GetDigitsFrac()) > frac {
+			to := new(types.MyDecimal)
+			err := dec.Round(to, frac, types.ModeHalfEven)
+			data = types.Datum{}
+			data.SetMysqlDecimal(to)
+			if err != nil {
+				return data, err
+			}
+		} else {
+			data = types.CloneDatum(v)
+		}
 	default:
 		var f float64
 		f, err = v.ToFloat64(sc)

expression/expr_to_pb.go

@@ -352,12 +352,31 @@ func (pc PbConverter) canFuncBePushed(sf *ScalarFunction) bool {
 
 		// date functions.
 		ast.DateFormat:
-		_, disallowPushdown := DefaultExprPushdownBlacklist.Load().(map[string]struct{})[sf.FuncName.L]
-		return true && !disallowPushdown
+		return isPushdownEnabled(sf.FuncName.L)
+
+	case ast.Cast:
+		// Disable time related cast function temporarily
+		switch sf.Function.PbCode() {
+		case tipb.ScalarFuncSig_CastIntAsTime,
+			tipb.ScalarFuncSig_CastRealAsTime,
+			tipb.ScalarFuncSig_CastDecimalAsTime,
+			tipb.ScalarFuncSig_CastStringAsTime,
+			tipb.ScalarFuncSig_CastDurationAsTime,
+			tipb.ScalarFuncSig_CastJsonAsTime,
+			tipb.ScalarFuncSig_CastTimeAsTime:
+			return false
+		default:
+			return isPushdownEnabled(sf.FuncName.L)
+		}
 	}
 	return false
 }
 
+func isPushdownEnabled(name string) bool {
+	_, disallowPushdown := DefaultExprPushdownBlacklist.Load().(map[string]struct{})[name]
+	return !disallowPushdown
+}
+
 // DefaultExprPushdownBlacklist indicates the expressions which can not be pushed down to TiKV.
 var DefaultExprPushdownBlacklist *atomic.Value
 

expression/expr_to_pb_test.go

@@ -266,6 +266,7 @@ func (s *testEvaluatorSuite) TestCompareFunc2Pb(c *C) {
 
 func (s *testEvaluatorSuite) TestLikeFunc2Pb(c *C) {
 	var likeFuncs []Expression
+	var expects []string
 	sc := new(stmtctx.StatementContext)
 	client := new(mock.Client)
 
@@ -280,19 +281,21 @@ func (s *testEvaluatorSuite) TestLikeFunc2Pb(c *C) {
 	}
 	ctx := mock.NewContext()
 	retTp = types.NewFieldType(mysql.TypeUnspecified)
-	fc, err := NewFunction(ctx, ast.Like, retTp, args[0], args[1], args[3])
+	fc1, err := NewFunction(ctx, ast.Like, retTp, args[0], args[1], args[3])
 	c.Assert(err, IsNil)
-	likeFuncs = append(likeFuncs, fc)
+	expects = append(expects, `{"tp":10000,"children":[{"tp":5,"val":"c3RyaW5n","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}},{"tp":5,"val":"cGF0dGVybg==","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}},{"tp":10000,"val":"CAA=","children":[{"tp":5,"val":"XA==","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}}],"sig":30,"field_type":{"tp":8,"flag":128,"flen":-1,"decimal":0,"collate":63,"charset":"binary"}}],"sig":4310,"field_type":{"tp":8,"flag":128,"flen":1,"decimal":0,"collate":63,"charset":"binary"}}`)
+	likeFuncs = append(likeFuncs, fc1)
 
-	fc, err = NewFunction(ctx, ast.Like, retTp, args[0], args[2], args[3])
+	fc2, err := NewFunction(ctx, ast.Like, retTp, args[0], args[2], args[3])
 	c.Assert(err, IsNil)
-	likeFuncs = append(likeFuncs, fc)
+	expects = append(expects, `{"tp":10000,"children":[{"tp":5,"val":"c3RyaW5n","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}},{"tp":5,"val":"JWFiYyU=","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}},{"tp":10000,"val":"CAA=","children":[{"tp":5,"val":"XA==","sig":0,"field_type":{"tp":254,"flag":0,"flen":-1,"decimal":-1,"collate":83,"charset":"utf8"}}],"sig":30,"field_type":{"tp":8,"flag":128,"flen":-1,"decimal":0,"collate":63,"charset":"binary"}}],"sig":4310,"field_type":{"tp":8,"flag":128,"flen":1,"decimal":0,"collate":63,"charset":"binary"}}`)
+	likeFuncs = append(likeFuncs, fc2)
 
 	pbExprs := ExpressionsToPBList(sc, likeFuncs, client)
-	for _, pbExpr := range pbExprs {
+	for i, pbExpr := range pbExprs {
 		js, err := json.Marshal(pbExpr)
 		c.Assert(err, IsNil)
-		c.Assert(string(js), Equals, "null")
+		c.Assert(string(js), Equals, expects[i])
 	}
 }
 
@@ -428,28 +431,29 @@ func (s *testEvaluatorSerialSuites) TestPushDownSwitcher(c *C) {
 	cases := []struct {
 		name   string
 		sig    tipb.ScalarFuncSig
+		argCnt int
 		enable bool
 	}{
-		{ast.And, tipb.ScalarFuncSig_BitAndSig, true},
-		{ast.Or, tipb.ScalarFuncSig_BitOrSig, false},
-		{ast.UnaryNot, tipb.ScalarFuncSig_UnaryNotInt, true},
+		{ast.And, tipb.ScalarFuncSig_BitAndSig, 2, true},
+		{ast.Or, tipb.ScalarFuncSig_BitOrSig, 2, false},
+		{ast.UnaryNot, tipb.ScalarFuncSig_UnaryNotInt, 1, true},
 	}
 	var enabled []string
-	for i, funcName := range cases {
-		args := []Expression{dg.genColumn(mysql.TypeLong, 1)}
-		if i+1 < len(cases) {
-			args = append(args, dg.genColumn(mysql.TypeLong, 2))
+	for _, cs := range cases {
+		args := make([]Expression, 0, cs.argCnt)
+		for i := 0; i < cs.argCnt; i++ {
+			args = append(args, dg.genColumn(mysql.TypeLong, int64(i)))
 		}
 		fc, err := NewFunction(
 			mock.NewContext(),
-			funcName.name,
+			cs.name,
 			types.NewFieldType(mysql.TypeUnspecified),
 			args...,
 		)
 		c.Assert(err, IsNil)
 		funcs = append(funcs, fc)
-		if funcName.enable {
-			enabled = append(enabled, funcName.name)
+		if cs.enable {
+			enabled = append(enabled, cs.name)
 		}
 	}
 

planner/core/logical_plan_test.go

@@ -86,7 +86,7 @@ func (s *testPlanSuite) TestPredicatePushDown(c *C) {
 		},
 		{
 			sql:  "select * from t t1, t t2 where t1.a = t2.b and t2.b > 0 and t1.a = t1.c and t1.d like 'abc' and t2.d = t1.d",
-			best: "Join{DataScan(t1)->Sel([like(cast(Column#4), abc, 92)])->DataScan(t2)->Sel([like(cast(Column#16), abc, 92)])}(Column#1,Column#14)(Column#4,Column#16)->Projection",
+			best: "Join{DataScan(t1)->DataScan(t2)}(Column#1,Column#14)(Column#4,Column#16)->Projection",
 		},
 		{
 			sql:  "select * from t ta join t tb on ta.d = tb.d and ta.d > 1 where tb.a = 0",

planner/core/testdata/plan_suite_out.json

@@ -1012,7 +1012,7 @@
       },
       {
         "SQL": "select a from t where c = 'hanfei'",
-        "Best": "IndexReader(Index(t.c_d_e)[[NULL,+inf]])->Sel([eq(cast(Column#3), cast(hanfei))])->Projection"
+        "Best": "IndexReader(Index(t.c_d_e)[[NULL,+inf]]->Sel([eq(cast(Column#3), cast(hanfei))]))->Projection"
       }
     ]
   },