f1e89cde19
*: rename github.com/Sirupsen/logrus to github.com/sirupsen/logrus * vendor: update pd * vendor: update github.com/pingcap/tipb/go-mysqlx
68 lines
1.9 KiB
Go
68 lines
1.9 KiB
Go
// Copyright 2016 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expression
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import (
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log "github.com/sirupsen/logrus"
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)
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// FoldConstant does constant folding optimization on an expression excluding deferred ones.
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func FoldConstant(expr Expression) Expression {
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e, _ := foldConstant(expr)
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return e
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}
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func foldConstant(expr Expression) (Expression, bool) {
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switch x := expr.(type) {
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case *ScalarFunction:
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if _, ok := unFoldableFunctions[x.FuncName.L]; ok {
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return expr, false
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}
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args := x.GetArgs()
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canFold := true
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isDeferredConst := false
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for i := 0; i < len(args); i++ {
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foldedArg, isDeferred := foldConstant(args[i])
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x.GetArgs()[i] = foldedArg
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_, conOK := foldedArg.(*Constant)
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if !conOK {
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canFold = false
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}
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isDeferredConst = isDeferredConst || isDeferred
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}
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if !canFold {
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return expr, isDeferredConst
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}
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value, err := x.Eval(nil)
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if err != nil {
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log.Warnf("fold constant %s: %s", x.ExplainInfo(), err.Error())
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return expr, isDeferredConst
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}
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if isDeferredConst {
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return &Constant{Value: value, RetType: x.RetType, DeferredExpr: x}, true
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}
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return &Constant{Value: value, RetType: x.RetType}, false
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case *Constant:
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if x.DeferredExpr != nil {
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value, err := x.DeferredExpr.Eval(nil)
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if err != nil {
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log.Warnf("fold constant %s: %s", x.ExplainInfo(), err.Error())
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return expr, true
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}
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return &Constant{Value: value, RetType: x.RetType, DeferredExpr: x.DeferredExpr}, true
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}
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}
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return expr, false
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}
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