mirror of https://github.com/tikv/client-go.git
125 lines
4.2 KiB
Go
125 lines
4.2 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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// See the License for the specific language governing permissions and
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// limitations under the License.
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package kv
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import "github.com/tikv/client-go/key"
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// Priority value for transaction priority.
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const (
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PriorityNormal = iota
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PriorityLow
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PriorityHigh
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)
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// IsoLevel is the transaction's isolation level.
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type IsoLevel int
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const (
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// SI stands for 'snapshot isolation'.
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SI IsoLevel = iota
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// RC stands for 'read committed'.
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RC
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)
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// Retriever is the interface wraps the basic Get and Seek methods.
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type Retriever interface {
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// Get gets the value for key k from kv store.
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// If corresponding kv pair does not exist, it returns nil and ErrNotExist.
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Get(k key.Key) ([]byte, error)
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// Iter creates an Iterator positioned on the first entry that k <= entry's key.
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// If such entry is not found, it returns an invalid Iterator with no error.
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// It yields only keys that < upperBound. If upperBound is nil, it means the upperBound is unbounded.
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// The Iterator must be closed after use.
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Iter(k key.Key, upperBound key.Key) (Iterator, error)
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// IterReverse creates a reversed Iterator positioned on the first entry which key is less than k.
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// The returned iterator will iterate from greater key to smaller key.
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// If k is nil, the returned iterator will be positioned at the last key.
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// TODO: Add lower bound limit
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IterReverse(k key.Key) (Iterator, error)
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}
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// Mutator is the interface wraps the basic Set and Delete methods.
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type Mutator interface {
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// Set sets the value for key k as v into kv store.
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// v must NOT be nil or empty, otherwise it returns ErrCannotSetNilValue.
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Set(k key.Key, v []byte) error
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// Delete removes the entry for key k from kv store.
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Delete(k key.Key) error
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}
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// RetrieverMutator is the interface that groups Retriever and Mutator interfaces.
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type RetrieverMutator interface {
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Retriever
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Mutator
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}
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// MemBuffer is an in-memory kv collection, can be used to buffer write operations.
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type MemBuffer interface {
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RetrieverMutator
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// Size returns sum of keys and values length.
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Size() int
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// Len returns the number of entries in the DB.
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Len() int
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// Reset cleanup the MemBuffer
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Reset()
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// SetCap sets the MemBuffer capability, to reduce memory allocations.
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// Please call it before you use the MemBuffer, otherwise it will not works.
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SetCap(cap int)
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}
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// Snapshot defines the interface for the snapshot fetched from KV store.
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type Snapshot interface {
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Retriever
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// BatchGet gets a batch of values from snapshot.
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BatchGet(keys []key.Key) (map[string][]byte, error)
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// SetPriority snapshot set the priority
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SetPriority(priority int)
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}
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// Iterator is the interface for a iterator on KV store.
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type Iterator interface {
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Valid() bool
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Key() key.Key
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Value() []byte
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Next() error
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Close()
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}
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// Transaction options
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const (
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// PresumeKeyNotExists indicates that when dealing with a Get operation but failing to read data from cache,
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// we presume that the key does not exist in Store. The actual existence will be checked before the
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// transaction's commit.
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// This option is an optimization for frequent checks during a transaction, e.g. batch inserts.
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PresumeKeyNotExists Option = iota + 1
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// PresumeKeyNotExistsError is the option key for error.
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// When PresumeKeyNotExists is set and condition is not match, should throw the error.
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PresumeKeyNotExistsError
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// BinlogInfo contains the binlog data and client.
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BinlogInfo
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// SchemaChecker is used for checking schema-validity.
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SchemaChecker
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// IsolationLevel sets isolation level for current transaction. The default level is SI.
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IsolationLevel
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// Priority marks the priority of this transaction.
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Priority
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// NotFillCache makes this request do not touch the LRU cache of the underlying storage.
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NotFillCache
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// SyncLog decides whether the WAL(write-ahead log) of this request should be synchronized.
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SyncLog
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// KeyOnly retrieve only keys, it can be used in scan now.
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KeyOnly
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)
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