expression: some builtin functions can be folded

expression/builtin.go

@@ -425,7 +425,7 @@ var funcs = map[string]functionClass{
 	ast.UnixTimestamp:    &unixTimestampFunctionClass{baseFunctionClass{ast.UnixTimestamp, 0, 1}},
 	ast.UTCDate:          &utcDateFunctionClass{baseFunctionClass{ast.UTCDate, 0, 0}},
 	ast.UTCTime:          &utcTimeFunctionClass{baseFunctionClass{ast.UTCTime, 0, 1}},
-	ast.UTCTimestamp:     &utcTimestampFunctionClass{baseFunctionClass{ast.UnixTimestamp, 0, 1}},
+	ast.UTCTimestamp:     &utcTimestampFunctionClass{baseFunctionClass{ast.UTCTimestamp, 0, 1}},
 	ast.Week:             &weekFunctionClass{baseFunctionClass{ast.Week, 1, 2}},
 	ast.Weekday:          &weekDayFunctionClass{baseFunctionClass{ast.Weekday, 1, 1}},
 	ast.WeekOfYear:       &weekOfYearFunctionClass{baseFunctionClass{ast.WeekOfYear, 1, 1}},

expression/builtin_info.go

@@ -63,7 +63,6 @@ func (c *databaseFunctionClass) getFunction(ctx context.Context, args []Expressi
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETString)
 	bf.tp.Flen = 64
-	bf.foldable = false
 	sig := &builtinDatabaseSig{bf}
 	return sig.setSelf(sig), nil
 }
@@ -119,7 +118,6 @@ func (c *currentUserFunctionClass) getFunction(ctx context.Context, args []Expre
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETString)
 	bf.tp.Flen = 64
-	bf.foldable = false
 	sig := &builtinCurrentUserSig{bf}
 	return sig.setSelf(sig), nil
 }
@@ -149,7 +147,6 @@ func (c *userFunctionClass) getFunction(ctx context.Context, args []Expression)
 		return nil, err
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETString)
-	bf.foldable = false
 	bf.tp.Flen = 64
 	sig := &builtinUserSig{bf}
 	return sig.setSelf(sig), nil
@@ -179,7 +176,6 @@ func (c *connectionIDFunctionClass) getFunction(ctx context.Context, args []Expr
 		return nil, err
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETInt)
-	bf.foldable = false
 	bf.tp.Flag |= mysql.UnsignedFlag
 	sig := &builtinConnectionIDSig{bf}
 	return sig.setSelf(sig), nil
@@ -212,7 +208,6 @@ func (c *lastInsertIDFunctionClass) getFunction(ctx context.Context, args []Expr
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETInt, argsTp...)
 	bf.tp.Flag |= mysql.UnsignedFlag
-	bf.foldable = false
 
 	if len(args) == 1 {
 		sig = &builtinLastInsertIDWithIDSig{bf}
@@ -260,7 +255,6 @@ func (c *versionFunctionClass) getFunction(ctx context.Context, args []Expressio
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETString)
 	bf.tp.Flen = 64
-	bf.foldable = false
 	sig := &builtinVersionSig{bf}
 	return sig.setSelf(sig), nil
 }

expression/builtin_info_test.go

@@ -33,7 +33,7 @@ func (s *testEvaluatorSuite) TestDatabase(c *C) {
 	ctx := mock.NewContext()
 	f, err := fc.getFunction(ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.Kind(), Equals, types.KindNull)
@@ -76,7 +76,7 @@ func (s *testEvaluatorSuite) TestUser(c *C) {
 	fc := funcs[ast.User]
 	f, err := fc.getFunction(ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.GetString(), Equals, "root@localhost")
@@ -91,7 +91,7 @@ func (s *testEvaluatorSuite) TestCurrentUser(c *C) {
 	fc := funcs[ast.CurrentUser]
 	f, err := fc.getFunction(ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.GetString(), Equals, "root@localhost")
@@ -106,7 +106,7 @@ func (s *testEvaluatorSuite) TestConnectionID(c *C) {
 	fc := funcs[ast.ConnectionID]
 	f, err := fc.getFunction(ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.GetUint64(), Equals, uint64(1))
@@ -117,7 +117,7 @@ func (s *testEvaluatorSuite) TestVersion(c *C) {
 	fc := funcs[ast.Version]
 	f, err := fc.getFunction(s.ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	v, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(v.GetString(), Equals, mysql.ServerVersion)
@@ -228,5 +228,5 @@ func (s *testEvaluatorSuite) TestLastInsertID(c *C) {
 
 	f, err := funcs[ast.LastInsertId].getFunction(s.ctx, []Expression{Zero})
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 }

expression/builtin_time.go

@@ -1659,7 +1659,6 @@ func (c *sysDateFunctionClass) getFunction(ctx context.Context, args []Expressio
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETDatetime, argTps...)
 	bf.tp.Flen, bf.tp.Decimal = 19, 0
-	bf.foldable = false
 
 	var sig builtinFunc
 	if len(args) == 1 {
@@ -1715,7 +1714,6 @@ func (c *currentDateFunctionClass) getFunction(ctx context.Context, args []Expre
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETDatetime)
 	bf.tp.Flen, bf.tp.Decimal = 10, 0
-	bf.foldable = false
 	sig := &builtinCurrentDateSig{bf}
 	return sig.setSelf(sig), nil
 }
@@ -1891,7 +1889,6 @@ func (c *utcDateFunctionClass) getFunction(ctx context.Context, args []Expressio
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETDatetime)
 	bf.tp.Flen, bf.tp.Decimal = 10, 0
-	bf.foldable = false
 	sig := &builtinUTCDateSig{bf}
 	return sig.setSelf(sig), nil
 }
@@ -1949,7 +1946,6 @@ func (c *utcTimestampFunctionClass) getFunction(ctx context.Context, args []Expr
 	} else {
 		bf.tp.Flen, bf.tp.Decimal = 19, 0
 	}
-	bf.foldable = false
 
 	var sig builtinFunc
 	if len(args) == 1 {
@@ -2852,7 +2848,6 @@ func (c *unixTimestampFunctionClass) getFunction(ctx context.Context, args []Exp
 	}
 
 	bf := newBaseBuiltinFuncWithTp(ctx, args, retTp, argTps...)
-	bf.foldable = false
 	bf.tp.Flen = retFLen
 	bf.tp.Decimal = retDecimal
 

expression/builtin_time_test.go

@@ -693,7 +693,7 @@ func (s *testEvaluatorSuite) TestNowAndUTCTimestamp(c *C) {
 		return tt
 	}
 
-	for i, x := range []struct {
+	for _, x := range []struct {
 		fc  functionClass
 		now func() time.Time
 	}{
@@ -702,11 +702,7 @@ func (s *testEvaluatorSuite) TestNowAndUTCTimestamp(c *C) {
 	} {
 		f, err := x.fc.getFunction(s.ctx, s.datumsToConstants(nil))
 		c.Assert(err, IsNil)
-		if i == 0 {
-			c.Assert(f.canBeFolded(), IsTrue)
-		} else {
-			c.Assert(f.canBeFolded(), IsFalse)
-		}
+		c.Assert(f.canBeFolded(), IsTrue)
 		v, err := f.eval(nil)
 		ts := x.now()
 		c.Assert(err, IsNil)
@@ -925,7 +921,7 @@ func (s *testEvaluatorSuite) TestSysDate(c *C) {
 		varsutil.SetSessionSystemVar(s.ctx.GetSessionVars(), "timestamp", timezone)
 		f, err := fc.getFunction(s.ctx, s.datumsToConstants(nil))
 		c.Assert(err, IsNil)
-		c.Assert(f.canBeFolded(), IsFalse)
+		c.Assert(f.canBeFolded(), IsTrue)
 		v, err := f.eval(nil)
 		last := time.Now()
 		c.Assert(err, IsNil)
@@ -1069,7 +1065,7 @@ func (s *testEvaluatorSuite) TestCurrentDate(c *C) {
 	fc := funcs[ast.CurrentDate]
 	f, err := fc.getFunction(mock.NewContext(), s.datumsToConstants(nil))
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	v, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	n := v.GetMysqlTime()
@@ -1466,7 +1462,7 @@ func (s *testEvaluatorSuite) TestUnixTimestamp(c *C) {
 	fc := funcs[ast.UnixTimestamp]
 	f, err := fc.getFunction(s.ctx, nil)
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err := f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.GetInt64()-time.Now().Unix(), GreaterEqual, int64(-1))
@@ -1493,7 +1489,7 @@ func (s *testEvaluatorSuite) TestUnixTimestamp(c *C) {
 	args = []types.Datum{types.NewDatum(nil)}
 	f, err = fc.getFunction(s.ctx, s.datumsToConstants(args))
 	c.Assert(err, IsNil)
-	c.Assert(f.canBeFolded(), IsFalse)
+	c.Assert(f.canBeFolded(), IsTrue)
 	d, err = f.eval(nil)
 	c.Assert(err, IsNil)
 	c.Assert(d.IsNull(), Equals, true)

plan/cacheable_checker.go

@@ -29,6 +29,26 @@ func Cacheable(node ast.Node) bool {
 	return checker.cacheable
 }
 
+var nonCacheableFunctions = map[string]struct{}{
+	ast.Now:              {},
+	ast.CurrentTimestamp: {},
+	ast.UTCTime:          {},
+	ast.Curtime:          {},
+	ast.CurrentTime:      {},
+	ast.UTCTimestamp:     {},
+	ast.UnixTimestamp:    {},
+	ast.Sysdate:          {},
+	ast.Curdate:          {},
+	ast.CurrentDate:      {},
+	ast.UTCDate:          {},
+	ast.Database:         {},
+	ast.CurrentUser:      {},
+	ast.User:             {},
+	ast.ConnectionID:     {},
+	ast.LastInsertId:     {},
+	ast.Version:          {},
+}
+
 // cacheableChecker checks whether a query's plan can be cached, querys that:
 //	 1. have ExistsSubqueryExpr, or
 //	 2. have VariableExpr
@@ -45,10 +65,7 @@ func (checker *cacheableChecker) Enter(in ast.Node) (out ast.Node, skipChildren
 		checker.cacheable = false
 		return in, true
 	case *ast.FuncCallExpr:
-		if node.FnName.L == ast.Now || node.FnName.L == ast.CurrentTimestamp ||
-			node.FnName.L == ast.UTCTime || node.FnName.L == ast.Curtime ||
-			node.FnName.L == ast.CurrentTime || node.FnName.L == ast.UTCTimestamp ||
-			node.FnName.L == ast.UnixTimestamp {
+		if _, found := nonCacheableFunctions[node.FnName.L]; found {
 			checker.cacheable = false
 			return in, true
 		}

plan/cacheable_checker_test.go

@@ -51,22 +51,12 @@ func (s *testCacheableSuite) TestCacheable(c *C) {
 	}
 	c.Assert(Cacheable(stmt), IsTrue)
 
-	whereExpr.FnName = model.NewCIStr("now")
-	c.Assert(Cacheable(stmt), IsFalse)
-
-	whereExpr.FnName = model.NewCIStr("current_timestamp")
-	c.Assert(Cacheable(stmt), IsFalse)
-
-	whereExpr.FnName = model.NewCIStr("utc_time")
-	c.Assert(Cacheable(stmt), IsFalse)
-
-	whereExpr.FnName = model.NewCIStr("curtime")
-	c.Assert(Cacheable(stmt), IsFalse)
-
-	whereExpr.FnName = model.NewCIStr("current_time")
-	c.Assert(Cacheable(stmt), IsFalse)
+	for funcName := range nonCacheableFunctions {
+		whereExpr.FnName = model.NewCIStr(funcName)
+		c.Assert(Cacheable(stmt), IsFalse)
+	}
 
-	whereExpr.FnName = model.NewCIStr("rand")
+	whereExpr.FnName = model.NewCIStr(ast.Rand)
 	c.Assert(Cacheable(stmt), IsTrue)
 
 	stmt = &ast.SelectStmt{