/
distinct.go
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/
distinct.go
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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
package command
import (
"context"
"github.com/mongodb/mongo-go-driver/bson"
"github.com/mongodb/mongo-go-driver/core/description"
"github.com/mongodb/mongo-go-driver/core/result"
"github.com/mongodb/mongo-go-driver/core/session"
"github.com/mongodb/mongo-go-driver/core/wiremessage"
"github.com/mongodb/mongo-go-driver/mongo/readconcern"
"github.com/mongodb/mongo-go-driver/mongo/readpref"
"github.com/mongodb/mongo-go-driver/x/bsonx"
)
// Distinct represents the disctinct command.
//
// The distinct command returns the distinct values for a specified field
// across a single collection.
type Distinct struct {
NS Namespace
Field string
Query bsonx.Doc
Opts []bsonx.Elem
ReadPref *readpref.ReadPref
ReadConcern *readconcern.ReadConcern
Clock *session.ClusterClock
Session *session.Client
result result.Distinct
err error
}
// Encode will encode this command into a wire message for the given server description.
func (d *Distinct) Encode(desc description.SelectedServer) (wiremessage.WireMessage, error) {
cmd, err := d.encode(desc)
if err != nil {
return nil, err
}
return cmd.Encode(desc)
}
// Encode will encode this command into a wire message for the given server description.
func (d *Distinct) encode(desc description.SelectedServer) (*Read, error) {
if err := d.NS.Validate(); err != nil {
return nil, err
}
command := bsonx.Doc{{"distinct", bsonx.String(d.NS.Collection)}, {"key", bsonx.String(d.Field)}}
if d.Query != nil {
command = append(command, bsonx.Elem{"query", bsonx.Document(d.Query)})
}
command = append(command, d.Opts...)
return &Read{
Clock: d.Clock,
DB: d.NS.DB,
ReadPref: d.ReadPref,
Command: command,
ReadConcern: d.ReadConcern,
Session: d.Session,
}, nil
}
// Decode will decode the wire message using the provided server description. Errors during decoding
// are deferred until either the Result or Err methods are called.
func (d *Distinct) Decode(desc description.SelectedServer, wm wiremessage.WireMessage) *Distinct {
rdr, err := (&Read{}).Decode(desc, wm).Result()
if err != nil {
d.err = err
return d
}
return d.decode(desc, rdr)
}
func (d *Distinct) decode(desc description.SelectedServer, rdr bson.Raw) *Distinct {
d.err = bson.Unmarshal(rdr, &d.result)
return d
}
// Result returns the result of a decoded wire message and server description.
func (d *Distinct) Result() (result.Distinct, error) {
if d.err != nil {
return result.Distinct{}, d.err
}
return d.result, nil
}
// Err returns the error set on this command.
func (d *Distinct) Err() error { return d.err }
// RoundTrip handles the execution of this command using the provided wiremessage.ReadWriter.
func (d *Distinct) RoundTrip(ctx context.Context, desc description.SelectedServer, rw wiremessage.ReadWriter) (result.Distinct, error) {
cmd, err := d.encode(desc)
if err != nil {
return result.Distinct{}, err
}
rdr, err := cmd.RoundTrip(ctx, desc, rw)
if err != nil {
return result.Distinct{}, err
}
return d.decode(desc, rdr).Result()
}