78 lines
1.7 KiB
Go
78 lines
1.7 KiB
Go
// Copyright 2015 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 plan
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import (
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"fmt"
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"math"
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"strings"
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)
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// Explain explains a Plan, returns description string.
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func Explain(p Plan) (string, error) {
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var e explainer
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p.Accept(&e)
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return strings.Join(e.strs, "->"), e.err
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}
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type explainer struct {
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strs []string
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err error
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}
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func (e *explainer) Enter(in Plan) (Plan, bool) {
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return in, false
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}
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func (e *explainer) Leave(in Plan) (Plan, bool) {
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var str string
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switch x := in.(type) {
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case *TableScan:
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if len(x.Ranges) > 0 {
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ran := x.Ranges[0]
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if ran.LowVal != math.MinInt64 || ran.HighVal != math.MaxInt64 {
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str = fmt.Sprintf("Range(%s)", x.Table.Name.L)
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} else {
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str = fmt.Sprintf("Table(%s)", x.Table.Name.L)
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}
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} else {
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str = fmt.Sprintf("Table(%s)", x.Table.Name.L)
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}
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case *IndexScan:
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str = fmt.Sprintf("Index(%s.%s)", x.Table.Name.L, x.Index.Name.L)
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case *ShowDDL:
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str = "ShowDDL"
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case *CheckTable:
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str = "CheckTable"
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case *Filter:
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str = "Filter"
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case *SelectFields:
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str = "Fields"
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case *Sort:
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if x.Bypass {
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return in, true
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}
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str = "Sort"
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case *SelectLock:
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str = "Lock"
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case *Limit:
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str = "Limit"
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default:
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e.err = ErrUnsupportedType.Gen("Unknown plan type %T", in)
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return in, false
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}
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e.strs = append(e.strs, str)
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return in, true
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}
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