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expression: refactor constant folding for IF&IFNULL (#9094)

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This commit is contained in:
Zhang Jian
2019-02-19 11:41:59 +08:00
committed by GitHub
parent bc0e70dc5c
commit 0ffb2f612c
2 changed files with 45 additions and 8 deletions
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18
expression/constant_fold.go
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@ -41,7 +41,10 @@ func ifFoldHandler(expr *ScalarFunction) (Expression, bool) {
if constArg, isConst := foldedArg0.(*Constant); isConst {
arg0, isNull0, err := constArg.EvalInt(expr.Function.getCtx(), chunk.Row{})
if err != nil {
log.Warnf("fold constant %s: %s", expr.ExplainInfo(), err.Error())
// Failed to fold this expr to a constant, print the DEBUG log and
// return the original expression to let the error to be evaluated
// again, in that time, the error is returned to the client.
log.Debugf("fold constant %s: %s", expr.ExplainInfo(), err.Error())
return expr, false
}
if !isNull0 && arg0 != 0 {
@ -59,16 +62,15 @@ func ifFoldHandler(expr *ScalarFunction) (Expression, bool) {
func ifNullFoldHandler(expr *ScalarFunction) (Expression, bool) {
args := expr.GetArgs()
foldedArg0, _ := foldConstant(args[0])
foldedArg0, isDeferred := foldConstant(args[0])
if constArg, isConst := foldedArg0.(*Constant); isConst {
_, isNull0, err := constArg.EvalInt(expr.Function.getCtx(), chunk.Row{})
if err != nil {
log.Warnf("fold constant %s: %s", expr.ExplainInfo(), err.Error())
return expr, false
}
if isNull0 {
// Only check constArg.Value here. Because deferred expression is
// evaluated to constArg.Value after foldConstant(args[0]), it's not
// needed to be checked.
if constArg.Value.IsNull() {
return foldConstant(args[1])
}
return constArg, isDeferred
}
var isDeferredConst bool
expr.GetArgs()[1], isDeferredConst = foldConstant(args[1])

35
expression/constant_fold_test.go Normal file
View File

@ -0,0 +1,35 @@
// Copyright 2019 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package expression_test
import (
. "github.com/pingcap/check"
"github.com/pingcap/tidb/util/testkit"
)
func (s *testIntegrationSuite) TestFoldIfNull(c *C) {
tk := testkit.NewTestKit(c, s.store)
tk.MustExec(`use test;`)
tk.MustExec(`drop table if exists t;`)
tk.MustExec(`create table t(a bigint, b bigint);`)
tk.MustExec(`insert into t values(1, 1);`)
tk.MustQuery(`desc select ifnull("aaaa", a) from t;`).Check(testkit.Rows(
`Projection_3 10000.00 root "aaaa"`,
`└─TableReader_5 10000.00 root data:TableScan_4`,
` └─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo`,
))
tk.MustQuery(`show warnings;`).Check(testkit.Rows())
tk.MustQuery(`select ifnull("aaaa", a) from t;`).Check(testkit.Rows("aaaa"))
tk.MustQuery(`show warnings;`).Check(testkit.Rows())
}