forked from pingcap/tidb
/
lock.go
85 lines (77 loc) · 2.32 KB
/
lock.go
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// Copyright 2015 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package plans
import (
"github.com/juju/errors"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/field"
"github.com/pingcap/tidb/parser/coldef"
"github.com/pingcap/tidb/plan"
"github.com/pingcap/tidb/util/format"
)
var (
_ plan.Plan = (*SelectLockPlan)(nil)
)
// SelectLockPlan handles SELECT ... FOR UPDATE, recording selected rows
// for acquiring locks explicitly.
type SelectLockPlan struct {
Src plan.Plan
Lock coldef.LockType
}
// Do implements plan.Plan Do interface, acquiring locks.
func (r *SelectLockPlan) Do(ctx context.Context, f plan.RowIterFunc) error {
return r.Src.Do(ctx, func(rid interface{}, in []interface{}) (bool, error) {
var rowKeys *RowKeyList
if in != nil && len(in) > 0 {
t := in[len(in)-1]
switch vt := t.(type) {
case *RowKeyList:
rowKeys = vt
// Remove row key list from data tail
in = in[:len(in)-1]
}
}
if rowKeys != nil && r.Lock == coldef.SelectLockForUpdate {
txn, err := ctx.GetTxn(false)
if err != nil {
return false, errors.Trace(err)
}
for _, k := range rowKeys.Keys {
err = txn.LockKeys([]byte(k.Key))
if err != nil {
return false, errors.Trace(err)
}
}
}
return f(rid, in)
})
}
// Explain implements plan.Plan Explain interface.
func (r *SelectLockPlan) Explain(w format.Formatter) {
r.Src.Explain(w)
if r.Lock != coldef.SelectLockForUpdate {
// no need to lock, just return.
return
}
w.Format("┌Lock row keys for update\n")
}
// GetFields implements plan.Plan GetFields interface.
func (r *SelectLockPlan) GetFields() []*field.ResultField {
return r.Src.GetFields()
}
// Filter implements plan.Plan Filter interface.
func (r *SelectLockPlan) Filter(ctx context.Context, expr expression.Expression) (plan.Plan, bool, error) {
// Do nothing
return r, false, nil
}