You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
51 lines
1.7 KiB
51 lines
1.7 KiB
// Copyright 2020 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 variable
|
|
|
|
import (
|
|
"sync"
|
|
)
|
|
|
|
// SequenceState cache all sequence's latest value accessed by lastval() builtins. It's a session scoped
|
|
// variable, and all public methods of SequenceState are currently-safe.
|
|
type SequenceState struct {
|
|
mu sync.Mutex
|
|
// latestValueMap caches the last value obtained by nextval() for each sequence id.
|
|
latestValueMap map[int64]int64
|
|
}
|
|
|
|
// NewSequenceState creates a SequenceState.
|
|
func NewSequenceState() *SequenceState {
|
|
return &SequenceState{mu: sync.Mutex{}, latestValueMap: make(map[int64]int64)}
|
|
}
|
|
|
|
// UpdateState will update the last value of specified sequenceID in a session.
|
|
func (ss *SequenceState) UpdateState(sequenceID, value int64) {
|
|
ss.mu.Lock()
|
|
defer ss.mu.Unlock()
|
|
ss.latestValueMap[sequenceID] = value
|
|
}
|
|
|
|
// GetLastValue will return last value of the specified sequenceID, bool(true) indicates
|
|
// the sequenceID is not in the cache map and NULL will be returned.
|
|
func (ss *SequenceState) GetLastValue(sequenceID int64) (int64, bool, error) {
|
|
ss.mu.Lock()
|
|
defer ss.mu.Unlock()
|
|
if len(ss.latestValueMap) > 0 {
|
|
if last, ok := ss.latestValueMap[sequenceID]; ok {
|
|
return last, false, nil
|
|
}
|
|
}
|
|
return 0, true, nil
|
|
}
|
|
|