75 lines
2.1 KiB
Go
75 lines
2.1 KiB
Go
// Copyright 2019 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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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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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// TODO combine with the pkg/kv package outside.
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package kv
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import (
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"context"
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"sync/atomic"
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"github.com/pingcap/tidb/pkg/meta/autoid"
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)
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// panickingAllocator is an ID allocator which panics on all operations except Rebase
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type panickingAllocator struct {
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autoid.Allocator
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base atomic.Int64
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ty autoid.AllocatorType
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}
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// NewPanickingAllocators creates a PanickingAllocator shared by all allocation types.
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// we use this to collect the max id(either _tidb_rowid or auto_increment id or auto_random) used
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// during import, and we will use this info to do ALTER TABLE xxx AUTO_RANDOM_BASE or AUTO_INCREMENT
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// on post-process phase.
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// TODO: support save all bases in checkpoint.
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func NewPanickingAllocators(sepAutoInc bool, base int64) autoid.Allocators {
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allocs := make([]autoid.Allocator, 0, 3)
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for _, t := range []autoid.AllocatorType{
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autoid.RowIDAllocType,
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autoid.AutoIncrementType,
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autoid.AutoRandomType,
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} {
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pa := &panickingAllocator{ty: t}
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pa.base.Store(base)
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allocs = append(allocs, pa)
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}
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return autoid.NewAllocators(sepAutoInc, allocs...)
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}
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// Rebase implements the autoid.Allocator interface
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func (alloc *panickingAllocator) Rebase(_ context.Context, newBase int64, _ bool) error {
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// CAS
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for {
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oldBase := alloc.base.Load()
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if newBase <= oldBase {
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break
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}
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if alloc.base.CompareAndSwap(oldBase, newBase) {
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break
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}
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}
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return nil
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}
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// Base implements the autoid.Allocator interface
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func (alloc *panickingAllocator) Base() int64 {
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return alloc.base.Load()
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}
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func (alloc *panickingAllocator) GetType() autoid.AllocatorType {
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return alloc.ty
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}
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