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// Copyright 2016 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 executor
import (
"context"
"github.com/cznic/mathutil"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/planner/core"
"github.com/pingcap/tidb/util/chunk"
)
// ExplainExec represents an explain executor.
type ExplainExec struct {
baseExecutor
explain *core.Explain
analyzeExec Executor
executed bool
rows [][]string
cursor int
}
// Open implements the Executor Open interface.
func (e *ExplainExec) Open(ctx context.Context) error {
if e.analyzeExec != nil {
return e.analyzeExec.Open(ctx)
}
return nil
}
// Close implements the Executor Close interface.
func (e *ExplainExec) Close() error {
e.rows = nil
return nil
}
// Next implements the Executor Next interface.
func (e *ExplainExec) Next(ctx context.Context, req *chunk.Chunk) error {
if e.rows == nil {
var err error
e.rows, err = e.generateExplainInfo(ctx)
if err != nil {
return err
}
}
req.GrowAndReset(e.maxChunkSize)
if e.cursor >= len(e.rows) {
return nil
}
numCurRows := mathutil.Min(req.Capacity(), len(e.rows)-e.cursor)
for i := e.cursor; i < e.cursor+numCurRows; i++ {
for j := range e.rows[i] {
req.AppendString(j, e.rows[i][j])
}
}
e.cursor += numCurRows
return nil
}
func (e *ExplainExec) executeAnalyzeExec(ctx context.Context) (err error) {
if e.analyzeExec != nil && !e.executed {
defer func() {
err1 := e.analyzeExec.Close()
if err1 != nil {
if err != nil {
err = errors.New(err.Error() + ", " + err1.Error())
} else {
err = err1
}
}
}()
e.executed = true
chk := newFirstChunk(e.analyzeExec)
for {
err = Next(ctx, e.analyzeExec, chk)
if err != nil || chk.NumRows() == 0 {
break
}
}
}
return err
}
func (e *ExplainExec) generateExplainInfo(ctx context.Context) (rows [][]string, err error) {
if err = e.executeAnalyzeExec(ctx); err != nil {
return nil, err
}
if err = e.explain.RenderResult(); err != nil {
return nil, err
}
return e.explain.Rows, nil
}
// getAnalyzeExecToExecutedNoDelay gets the analyze DML executor to execute in handleNoDelay function.
// For explain analyze insert/update/delete statement, the analyze executor should be executed in handleNoDelay
// function and then commit transaction if needed.
// Otherwise, in autocommit transaction, the table record change of analyze executor(insert/update/delete...)
// will not be committed.
func (e *ExplainExec) getAnalyzeExecToExecutedNoDelay() Executor {
if e.analyzeExec != nil && !e.executed && e.analyzeExec.Schema().Len() == 0 {
e.executed = true
return e.analyzeExec
}
return nil
}