mirror of
https://github.com/go-gitea/gitea.git
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173 lines
5.4 KiB
Go
173 lines
5.4 KiB
Go
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// 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 kv
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import "io"
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const (
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// PresumeKeyNotExists directives 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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)
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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) ([]byte, error)
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// Seek 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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// The Iterator must be Closed after use.
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Seek(k 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, v []byte) error
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// Delete removes the entry for key k from kv store.
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Delete(k 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. It should be released after use.
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type MemBuffer interface {
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RetrieverMutator
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// Release releases the buffer.
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Release()
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}
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// Transaction defines the interface for operations inside a Transaction.
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// This is not thread safe.
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type Transaction interface {
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RetrieverMutator
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// Commit commits the transaction operations to KV store.
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Commit() error
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// Rollback undoes the transaction operations to KV store.
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Rollback() error
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// String implements fmt.Stringer interface.
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String() string
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// LockKeys tries to lock the entries with the keys in KV store.
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LockKeys(keys ...Key) error
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// SetOption sets an option with a value, when val is nil, uses the default
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// value of this option.
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SetOption(opt Option, val interface{})
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// DelOption deletes an option.
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DelOption(opt Option)
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// IsReadOnly checks if the transaction has only performed read operations.
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IsReadOnly() bool
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// GetClient gets a client instance.
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GetClient() Client
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// StartTS returns the transaction start timestamp.
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StartTS() int64
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}
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// Client is used to send request to KV layer.
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type Client interface {
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// Send sends request to KV layer, returns a Response.
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Send(req *Request) Response
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// SupportRequestType checks if reqType and subType is supported.
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SupportRequestType(reqType, subType int64) bool
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}
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// ReqTypes.
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const (
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ReqTypeSelect = 101
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ReqTypeIndex = 102
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)
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// KeyRange represents a range where StartKey <= key < EndKey.
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type KeyRange struct {
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StartKey Key
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EndKey Key
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}
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// Request represents a kv request.
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type Request struct {
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// The request type.
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Tp int64
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Data []byte
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// Key Ranges
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KeyRanges []KeyRange
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// If desc is true, the request is sent in descending order.
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Desc bool
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// If concurrency is 1, it only sends the request to a single storage unit when
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// ResponseIterator.Next is called. If concurrency is greater than 1, the request will be
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// sent to multiple storage units concurrently.
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Concurrency int
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}
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// Response represents the response returned from KV layer.
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type Response interface {
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// Next returns a resultSubset from a single storage unit.
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// When full result set is returned, nil is returned.
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Next() (resultSubset io.ReadCloser, err error)
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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) (map[string][]byte, error)
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// Release releases the snapshot to store.
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Release()
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}
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// Driver is the interface that must be implemented by a KV storage.
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type Driver interface {
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// Open returns a new Storage.
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// The path is the string for storage specific format.
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Open(path string) (Storage, error)
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}
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// Storage defines the interface for storage.
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// Isolation should be at least SI(SNAPSHOT ISOLATION)
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type Storage interface {
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// Begin transaction
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Begin() (Transaction, error)
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// GetSnapshot gets a snapshot that is able to read any data which data is <= ver.
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// if ver is MaxVersion or > current max committed version, we will use current version for this snapshot.
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GetSnapshot(ver Version) (Snapshot, error)
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// Close store
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Close() error
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// Storage's unique ID
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UUID() string
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// CurrentVersion returns current max committed version.
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CurrentVersion() (Version, error)
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}
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// FnKeyCmp is the function for iterator the keys
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type FnKeyCmp func(key Key) bool
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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
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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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