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// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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package readconcern // import "go.mongodb.org/mongo-driver/mongo/readconcern"
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import (
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"go.mongodb.org/mongo-driver/bson/bsontype"
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"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
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)
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// ReadConcern for replica sets and replica set shards determines which data to return from a query.
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type ReadConcern struct {
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level string
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}
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// Option is an option to provide when creating a ReadConcern.
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type Option func(concern *ReadConcern)
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// Level creates an option that sets the level of a ReadConcern.
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func Level(level string) Option {
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return func(concern *ReadConcern) {
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concern.level = level
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}
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}
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// Local specifies that the query should return the instance’s most recent data.
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func Local() *ReadConcern {
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return New(Level("local"))
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}
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// Majority specifies that the query should return the instance’s most recent data acknowledged as
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// having been written to a majority of members in the replica set.
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func Majority() *ReadConcern {
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return New(Level("majority"))
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}
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// Linearizable specifies that the query should return data that reflects all successful writes
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// issued with a write concern of "majority" and acknowledged prior to the start of the read operation.
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func Linearizable() *ReadConcern {
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return New(Level("linearizable"))
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}
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// Available specifies that the query should return data from the instance with no guarantee
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// that the data has been written to a majority of the replica set members (i.e. may be rolled back).
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func Available() *ReadConcern {
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return New(Level("available"))
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}
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// Snapshot is only available for operations within multi-document transactions.
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func Snapshot() *ReadConcern {
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return New(Level("snapshot"))
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}
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// New constructs a new read concern from the given string.
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func New(options ...Option) *ReadConcern {
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concern := &ReadConcern{}
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for _, option := range options {
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option(concern)
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}
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return concern
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}
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// MarshalBSONValue implements the bson.ValueMarshaler interface.
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func (rc *ReadConcern) MarshalBSONValue() (bsontype.Type, []byte, error) {
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var elems []byte
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if len(rc.level) > 0 {
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elems = bsoncore.AppendStringElement(elems, "level", rc.level)
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}
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return bsontype.EmbeddedDocument, bsoncore.BuildDocument(nil, elems), nil
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}
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// GetLevel returns the read concern level.
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func (rc *ReadConcern) GetLevel() string {
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return rc.level
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}
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