tidb cte_table_reader 源码
tidb cte_table_reader 代码
文件路径：/executor/cte_table_reader.go
// Copyright 2021 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package executor
import (
"context"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/cteutil"
)
// CTETableReaderExec scans data in iterInTbl, which is filled by corresponding CTEExec.
type CTETableReaderExec struct {
baseExecutor
iterInTbl cteutil.Storage
chkIdx int
curIter int
}
// Open implements the Executor interface.
func (e *CTETableReaderExec) Open(ctx context.Context) error {
e.reset()
return e.baseExecutor.Open(ctx)
}
// Next implements the Executor interface.
func (e *CTETableReaderExec) Next(ctx context.Context, req *chunk.Chunk) (err error) {
req.Reset()
// We should read `iterInTbl` from the beginning when the next iteration starts.
// Can not directly judge whether to start the next iteration based on e.chkIdx,
// because some operators(Selection) may use for loop to read all data in `iterInTbl`.
if e.curIter != e.iterInTbl.GetIter() {
if e.curIter > e.iterInTbl.GetIter() {
return errors.Errorf("invalid iteration for CTETableReaderExec (e.curIter: %d, e.iterInTbl.GetIter(): %d)",
e.curIter, e.iterInTbl.GetIter())
}
e.chkIdx = 0
e.curIter = e.iterInTbl.GetIter()
}
if e.chkIdx < e.iterInTbl.NumChunks() {
res, err := e.iterInTbl.GetChunk(e.chkIdx)
if err != nil {
return err
}
// Need to copy chunk to make sure upper operators will not change chunk in iterInTbl.
req.SwapColumns(res.CopyConstructSel())
e.chkIdx++
}
return nil
}
// Close implements the Executor interface.
func (e *CTETableReaderExec) Close() (err error) {
e.reset()
return e.baseExecutor.Close()
}
func (e *CTETableReaderExec) reset() {
e.chkIdx = 0
e.curIter = 0
}
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