82 lines
1.9 KiB
Go
82 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 executor
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import (
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"encoding/json"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/plan"
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"github.com/pingcap/tidb/util/types"
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)
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// ExplainExec represents an explain executor.
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// See https://dev.mysql.com/doc/refman/5.7/en/explain-output.html
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type ExplainExec struct {
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StmtPlan plan.Plan
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schema *expression.Schema
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rows []*Row
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cursor int
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}
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// Schema implements the Executor Schema interface.
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func (e *ExplainExec) Schema() *expression.Schema {
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return e.schema
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}
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func (e *ExplainExec) prepareExplainInfo(p plan.Plan, parent plan.Plan) error {
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for _, child := range p.Children() {
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err := e.prepareExplainInfo(child, p)
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if err != nil {
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return errors.Trace(err)
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}
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}
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explain, err := json.MarshalIndent(p, "", " ")
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if err != nil {
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return errors.Trace(err)
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}
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parentStr := ""
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if parent != nil {
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parentStr = parent.ID()
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}
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row := &Row{
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Data: types.MakeDatums(p.ID(), string(explain), parentStr),
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}
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e.rows = append(e.rows, row)
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return nil
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}
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// Next implements Execution Next interface.
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func (e *ExplainExec) Next() (*Row, error) {
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if e.cursor == 0 {
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err := e.prepareExplainInfo(e.StmtPlan, nil)
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if err != nil {
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return nil, errors.Trace(err)
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}
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}
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if e.cursor >= len(e.rows) {
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return nil, nil
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}
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row := e.rows[e.cursor]
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e.cursor++
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return row, nil
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}
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// Close implements the Executor Close interface.
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func (e *ExplainExec) Close() error {
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e.rows = nil
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return nil
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}
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