123 lines
3.4 KiB
Go
123 lines
3.4 KiB
Go
// Copyright 2018 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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"github.com/juju/errors"
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"github.com/pingcap/tidb/kv"
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"github.com/pingcap/tidb/types"
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"github.com/pingcap/tidb/util/chunk"
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"golang.org/x/net/context"
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)
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// ReplaceExec represents a replace executor.
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type ReplaceExec struct {
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*InsertValues
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Priority int
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finished bool
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}
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// Close implements the Executor Close interface.
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func (e *ReplaceExec) Close() error {
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if e.SelectExec != nil {
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return e.SelectExec.Close()
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}
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return nil
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}
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// Open implements the Executor Open interface.
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func (e *ReplaceExec) Open(ctx context.Context) error {
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if e.SelectExec != nil {
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return e.SelectExec.Open(ctx)
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}
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return nil
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}
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func (e *ReplaceExec) exec(rows []types.DatumRow) error {
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/*
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* MySQL uses the following algorithm for REPLACE (and LOAD DATA ... REPLACE):
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* 1. Try to insert the new row into the table
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* 2. While the insertion fails because a duplicate-key error occurs for a primary key or unique index:
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* 3. Delete from the table the conflicting row that has the duplicate key value
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* 4. Try again to insert the new row into the table
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* See http://dev.mysql.com/doc/refman/5.7/en/replace.html
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*
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* For REPLACE statements, the affected-rows value is 2 if the new row replaced an old row,
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* because in this case, one row was inserted after the duplicate was deleted.
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* See http://dev.mysql.com/doc/refman/5.7/en/mysql-affected-rows.html
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*/
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idx := 0
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rowsLen := len(rows)
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sc := e.ctx.GetSessionVars().StmtCtx
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for {
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if idx >= rowsLen {
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break
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}
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row := rows[idx]
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h, err1 := e.Table.AddRecord(e.ctx, row, false)
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if err1 == nil {
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e.ctx.StmtAddDirtyTableOP(DirtyTableAddRow, e.Table.Meta().ID, h, row)
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idx++
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continue
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}
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if err1 != nil && !kv.ErrKeyExists.Equal(err1) {
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return errors.Trace(err1)
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}
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oldRow, err1 := e.Table.Row(e.ctx, h)
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if err1 != nil {
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return errors.Trace(err1)
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}
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rowUnchanged, err1 := types.EqualDatums(sc, oldRow, row)
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if err1 != nil {
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return errors.Trace(err1)
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}
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if rowUnchanged {
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// If row unchanged, we do not need to do insert.
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e.ctx.GetSessionVars().StmtCtx.AddAffectedRows(1)
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idx++
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continue
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}
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// Remove current row and try replace again.
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err1 = e.Table.RemoveRecord(e.ctx, h, oldRow)
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if err1 != nil {
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return errors.Trace(err1)
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}
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e.ctx.StmtAddDirtyTableOP(DirtyTableDeleteRow, e.Table.Meta().ID, h, nil)
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e.ctx.GetSessionVars().StmtCtx.AddAffectedRows(1)
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}
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if e.lastInsertID != 0 {
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e.ctx.GetSessionVars().SetLastInsertID(e.lastInsertID)
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}
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e.finished = true
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return nil
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}
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// Next implements the Executor Next interface.
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func (e *ReplaceExec) Next(ctx context.Context, chk *chunk.Chunk) error {
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chk.Reset()
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if e.finished {
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return nil
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}
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cols, err := e.getColumns(e.Table.Cols())
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if err != nil {
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return errors.Trace(err)
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}
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if len(e.children) > 0 && e.children[0] != nil {
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return errors.Trace(e.insertRowsFromSelect(ctx, cols, e.exec))
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}
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return errors.Trace(e.insertRows(cols, e.exec))
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}
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