Execute a database command that reads

# MongoDB\Driver\Manager::executeReadCommand

(mongodb >=1.4.0)

MongoDB\Driver\Manager::executeReadCommand — Execute a database command that reads

### 説明

final public MongoDB\Driver\Manager::executeReadCommand ( string `$db` , MongoDB\Driver\Command `$command` [, array `$options` = array() ] ) : MongoDB\Driver\Cursor

Selects a server according to the "readPreference" option and executes the command on that server. By default, the read preference from the MongoDB Connection URI will be used.

This method will apply logic that is specific to commands that read (e.g. » count) and take the MongoDB server version into account. The "readConcern" option will default to the corresponding value from the MongoDB Connection URI.

### パラメータ

`db` (string)

  コマンドを実行するデータベースの名前。

`command` (MongoDB\Driver\Command)

  実行するコマンド。

`options`

  options
  Option | Type | Description
  --- | --- | ---
  readConcern | MongoDB\Driver\ReadConcern | A read concern to apply to the operation. This option is available in MongoDB 3.2+ and will result in an exception at execution time if specified for an older server version.
  readPreference | MongoDB\Driver\ReadPreference | A read preference to use for selecting a server for the operation.
  session | MongoDB\Driver\Session | A session to associate with the operation.

  警告

  If you are using a "session" which has a transaction in progress, you cannot specify a "readConcern" or "writeConcern" option. This will result in an MongoDB\Driver\Exception\InvalidArgumentException being thrown. Instead, you should set these two options when you create the transaction with MongoDB\Driver\Session::startTransaction().

### 返り値

成功した場合に MongoDB\Driver\Cursor を返します。

### エラー / 例外

- Throws MongoDB\Driver\Exception\InvalidArgumentException if the "session" option is used with an associated transaction in combination with a "readConcern" or "writeConcern" option.
- 引数のパースに失敗した場合に MongoDB\Driver\Exception\InvalidArgumentException をスローします。
- サーバーへの接続が認証以外の理由で失敗した場合に MongoDB\Driver\Exception\ConnectionException をスローします。
- 認証が必要な場面で認証に失敗した場合に MongoDB\Driver\Exception\AuthenticationException をスローします。
- Throws MongoDB\Driver\Exception\RuntimeException on other errors (e.g. invalid command).

### 参考

- MongoDB\Driver\Command
- MongoDB\Driver\Cursor
- MongoDB\Driver\Manager::executeCommand() - Execute a database command
- MongoDB\Driver\Manager::executeReadWriteCommand() - Execute a database command that reads and writes
- MongoDB\Driver\Manager::executeWriteCommand() - Execute a database command that writes
- MongoDB\Driver\Server::executeReadCommand() - Execute a database command that reads on this server