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180 lines
4.2 KiB
180 lines
4.2 KiB
// Copyright 2015 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 autoid
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import (
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"sync"
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"github.com/juju/errors"
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"github.com/ngaut/log"
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"github.com/pingcap/tidb/kv"
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"github.com/pingcap/tidb/meta"
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)
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const (
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step = 1000
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)
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// Allocator is an auto increment id generator.
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// Just keep id unique actually.
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type Allocator interface {
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// Alloc allocs the next autoID for table with tableID.
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// It gets a batch of autoIDs at a time. So it does not need to access storage for each call.
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Alloc(tableID int64) (int64, error)
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// Rebase rebases the autoID base for table with tableID and the new base value.
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// If allocIDs is true, it will allocate some IDs and save to the cache.
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// If allocIDs is false, it will not allocate IDs.
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Rebase(tableID, newBase int64, allocIDs bool) error
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}
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type allocator struct {
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mu sync.Mutex
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base int64
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end int64
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store kv.Storage
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dbID int64
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}
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// Rebase implements autoid.Allocator Rebase interface.
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func (alloc *allocator) Rebase(tableID, newBase int64, allocIDs bool) error {
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if tableID == 0 {
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return errors.New("Invalid tableID")
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}
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alloc.mu.Lock()
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defer alloc.mu.Unlock()
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if newBase <= alloc.base {
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return nil
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}
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if newBase <= alloc.end {
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alloc.base = newBase
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return nil
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}
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return kv.RunInNewTxn(alloc.store, true, func(txn kv.Transaction) error {
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m := meta.NewMeta(txn)
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end, err := m.GetAutoTableID(alloc.dbID, tableID)
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if err != nil {
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return errors.Trace(err)
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}
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if newBase <= end {
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return nil
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}
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newStep := newBase - end + step
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if !allocIDs {
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newStep = newBase - end
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}
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end, err = m.GenAutoTableID(alloc.dbID, tableID, newStep)
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if err != nil {
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return errors.Trace(err)
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}
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alloc.end = end
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alloc.base = newBase
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if !allocIDs {
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alloc.base = alloc.end
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}
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return nil
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})
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}
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// Alloc implements autoid.Allocator Alloc interface.
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func (alloc *allocator) Alloc(tableID int64) (int64, error) {
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if tableID == 0 {
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return 0, errors.New("Invalid tableID")
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}
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alloc.mu.Lock()
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defer alloc.mu.Unlock()
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if alloc.base == alloc.end { // step
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err := kv.RunInNewTxn(alloc.store, true, func(txn kv.Transaction) error {
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m := meta.NewMeta(txn)
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base, err1 := m.GetAutoTableID(alloc.dbID, tableID)
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if err1 != nil {
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return errors.Trace(err1)
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}
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end, err1 := m.GenAutoTableID(alloc.dbID, tableID, step)
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if err1 != nil {
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return errors.Trace(err1)
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}
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alloc.end = end
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if end == step {
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alloc.base = base
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} else {
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alloc.base = end - step
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}
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return nil
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})
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if err != nil {
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return 0, errors.Trace(err)
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}
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}
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alloc.base++
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log.Debugf("[kv] Alloc id %d, table ID:%d, from %p, database ID:%d", alloc.base, tableID, alloc, alloc.dbID)
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return alloc.base, nil
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}
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var (
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memID int64
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memIDLock sync.Mutex
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)
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type memoryAllocator struct {
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mu sync.Mutex
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base int64
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end int64
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dbID int64
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}
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// Rebase implements autoid.Allocator Rebase interface.
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func (alloc *memoryAllocator) Rebase(tableID, newBase int64, allocIDs bool) error {
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// TODO: implement it.
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return nil
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}
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// Alloc implements autoid.Allocator Alloc interface.
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func (alloc *memoryAllocator) Alloc(tableID int64) (int64, error) {
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if tableID == 0 {
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return 0, errors.New("Invalid tableID")
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}
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alloc.mu.Lock()
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defer alloc.mu.Unlock()
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if alloc.base == alloc.end { // step
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memIDLock.Lock()
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memID = memID + step
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alloc.end = memID
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alloc.base = alloc.end - step
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memIDLock.Unlock()
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}
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alloc.base++
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return alloc.base, nil
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}
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// NewAllocator returns a new auto increment id generator on the store.
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func NewAllocator(store kv.Storage, dbID int64) Allocator {
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return &allocator{
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store: store,
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dbID: dbID,
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}
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}
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// NewMemoryAllocator returns a new auto increment id generator in memory.
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func NewMemoryAllocator(dbID int64) Allocator {
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return &memoryAllocator{
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dbID: dbID,
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}
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}
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