58 lines
1.4 KiB
Go
58 lines
1.4 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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evaluated bool
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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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// Next implements Execution Next interface.
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func (e *ExplainExec) Next() (*Row, error) {
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if e.evaluated {
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return nil, nil
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}
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e.evaluated = true
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explain, err := json.MarshalIndent(e.StmtPlan, "", " ")
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if err != nil {
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return nil, errors.Trace(err)
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}
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row := &Row{
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Data: types.MakeDatums("EXPLAIN", string(explain)),
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}
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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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return nil
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}
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