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delete.go
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delete.go
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// Copyright 2015 The Cockroach Authors.
//
// 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.
//
// Author: Peter Mattis (peter@cockroachlabs.com)
package sql
import (
"bytes"
"fmt"
"github.com/cockroachdb/cockroach/client"
"github.com/cockroachdb/cockroach/roachpb"
"github.com/cockroachdb/cockroach/sql/parser"
"github.com/cockroachdb/cockroach/sql/privilege"
"github.com/cockroachdb/cockroach/util/log"
)
type deleteNode struct {
editNodeBase
n *parser.Delete
run struct {
// The following fields are populated during Start().
editNodeRun
rd rowDeleter
fastPath bool
}
}
// Delete removes rows from a table.
// Privileges: DELETE and SELECT on table. We currently always use a SELECT statement.
// Notes: postgres requires DELETE. Also requires SELECT for "USING" and "WHERE" with tables.
// mysql requires DELETE. Also requires SELECT if a table is used in the "WHERE" clause.
func (p *planner) Delete(n *parser.Delete, autoCommit bool) (planNode, *roachpb.Error) {
en, pErr := p.makeEditNode(n.Table, n.Returning, autoCommit, privilege.DELETE)
if pErr != nil {
return nil, pErr
}
// TODO(knz): Until we split the creation of the node from Start()
// for the SelectClause too, we cannot cache this. This is because
// this node's initSelect() method both does type checking and also
// performs index selection. We cannot perform index selection
// properly until the placeholder values are known.
_, pErr = p.SelectClause(&parser.SelectClause{
Exprs: en.tableDesc.allColumnsSelector(),
From: []parser.TableExpr{n.Table},
Where: n.Where,
})
if pErr != nil {
return nil, pErr
}
if pErr := en.rh.TypeCheck(); pErr != nil {
return nil, pErr
}
return &deleteNode{
n: n,
editNodeBase: en,
}, nil
}
func (d *deleteNode) Start() *roachpb.Error {
// TODO(knz): See the comment above in Delete().
rows, pErr := d.p.SelectClause(&parser.SelectClause{
Exprs: d.tableDesc.allColumnsSelector(),
From: []parser.TableExpr{d.n.Table},
Where: d.n.Where,
})
if pErr != nil {
return pErr
}
if pErr := rows.Start(); pErr != nil {
return pErr
}
// Construct a map from column ID to the index the value appears at within a
// row.
colIDtoRowIndex, err := makeColIDtoRowIndex(rows, d.tableDesc)
if err != nil {
return roachpb.NewError(err)
}
rd, err := makeRowDeleter(d.tableDesc, colIDtoRowIndex)
if err != nil {
return roachpb.NewError(err)
}
d.run.rd = rd
d.run.startEditNode(&d.editNodeBase, rows)
// Check if we can avoid doing a round-trip to read the values and just
// "fast-path" skip to deleting the key ranges without reading them first.
// TODO(dt): We could probably be smarter when presented with an index-join,
// but this goes away anyway once we push-down more of SQL.
sel := rows.(*selectNode)
if scan, ok := sel.table.node.(*scanNode); ok && canDeleteWithoutScan(d.n, scan, d.run.rd) {
d.run.fastPath = true
d.run.pErr = d.fastDelete()
d.run.done = true
return d.run.pErr
}
return nil
}
func (d *deleteNode) FastPathResults() (int, bool) {
if d.run.fastPath {
return d.rh.rowCount, true
}
return 0, false
}
func (d *deleteNode) Next() bool {
if d.run.done || d.run.pErr != nil {
return false
}
if !d.run.rows.Next() {
// We're done. Finish the batch.
d.run.finalize(&d.editNodeBase, false)
return false
}
rowVals := d.run.rows.Values()
d.run.pErr = d.run.rd.DeleteRow(d.run.b, rowVals)
if d.run.pErr != nil {
return false
}
resultRow, err := d.rh.cookResultRow(rowVals)
if err != nil {
d.run.pErr = roachpb.NewError(err)
return false
}
d.run.resultRow = resultRow
return true
}
// Determine if the deletion of `rows` can be done without actually scanning them,
// i.e. if we do not need to know their values for filtering expressions or a
// RETURNING clause or for updating secondary indexes.
func canDeleteWithoutScan(n *parser.Delete, scan *scanNode, rd rowDeleter) bool {
if !rd.HasFast() {
return false
}
if n.Returning != nil {
if log.V(2) {
log.Infof("delete forced to scan: values required for RETURNING")
}
return false
}
if scan.filter != nil {
if log.V(2) {
log.Infof("delete forced to scan: values required for filter (%s)", scan.filter)
}
return false
}
return true
}
// `fastDelete` skips the scan of rows and just deletes the ranges that
// `rows` would scan. Should only be used if `canDeleteWithoutScan` indicates
// that it is safe to do so.
func (d *deleteNode) fastDelete() *roachpb.Error {
scan := d.run.rows.(*selectNode).table.node.(*scanNode)
if !scan.initScan() {
return scan.pErr
}
rowCount, pErr := d.run.rd.FastDelete(d.run.b, scan, d.fastDeleteCommitFunc)
if pErr != nil {
return pErr
}
d.rh.rowCount += rowCount
return nil
}
func (d *deleteNode) fastDeleteCommitFunc(b *client.Batch) *roachpb.Error {
if d.autoCommit {
// An auto-txn can commit the transaction with the batch. This is an
// optimization to avoid an extra round-trip to the transaction
// coordinator.
if pErr := d.p.txn.CommitInBatch(b); pErr != nil {
return pErr
}
} else {
if pErr := d.p.txn.Run(b); pErr != nil {
return pErr
}
}
return nil
}
func (d *deleteNode) Columns() []ResultColumn {
return d.rh.columns
}
func (d *deleteNode) Values() parser.DTuple {
return d.run.resultRow
}
func (d *deleteNode) MarkDebug(mode explainMode) {
d.run.rows.MarkDebug(mode)
}
func (d *deleteNode) DebugValues() debugValues {
return d.run.rows.DebugValues()
}
func (d *deleteNode) Ordering() orderingInfo {
return d.run.rows.Ordering()
}
func (d *deleteNode) PErr() *roachpb.Error {
return d.run.pErr
}
func (d *deleteNode) ExplainPlan(v bool) (name, description string, children []planNode) {
var buf bytes.Buffer
if v {
fmt.Fprintf(&buf, "from %s returning (", d.tableDesc.Name)
for i, col := range d.rh.columns {
if i > 0 {
fmt.Fprintf(&buf, ", ")
}
fmt.Fprintf(&buf, "%s", col.Name)
}
fmt.Fprintf(&buf, ")")
}
return "delete", buf.String(), []planNode{d.run.rows}
}
func (d *deleteNode) SetLimitHint(numRows int64, soft bool) {}