Cassandra用datastax php驅動程序編寫語句錯誤

Question

我用DataStax php驅動程序1.0.0-rc和Cassandra 2.2.3編寫的語句面臨奇怪的錯誤。我在這條線的異常：

$statement = $this->session->prepare("SELECT ? FROM ? WHERE ? = ?"); 

我看到這個錯誤：

"error_code":33562624 
"error_message":"Bind variables cannot be used for keyspace names" 

下面使用卡桑德拉到comunicate類的存根：

class ClsCassandra extends ClsDbObject 
{ 
    private $hostname=""; 
    private $username=""; 
    private $password=""; 
    private $keyspace=""; 
    private $poi_table=""; 
    private $poi_table_key_field=""; 
    private $poi_table_content_field=""; 

    private $cluster = NULL; 
    private $session = NULL; 

    private $threads = 1; 

    function __construct() 
    { 
     ... 
     ... 
     // 
     // i set up all the properties above 
     // 
     ... 
     ... 
    } 

    public function runQuery(&$error) 
    { 
     try 
     {   
      $this->cluster = Cassandra::cluster() 
      ->withContactPoints($this->hostname) 
      ->withCredentials($this->username, $this->password) 
      ->withIOThreads($this->threads) 
      ->build(); 

      $this->session = $this->cluster->connect($this->keyspace); 

      // error on next line... 
      $statement = $this->session->prepare("SELECT ? FROM ? WHERE ? = ?"); 
      $results = $this->session->execute($statement, new Cassandra\ExecutionOptions(array(
        'arguments' => array($this->poi_table_content_field, $this->poi_table, $this->poi_table_key_field, $keypattern) 
      ))); 

     } 
     catch(Cassandra\Exception $ce) 
     { 
      $error->setError($ce->getCode(), $ce->getMessage(), $ce->getTraceAsString()); 
      $this->log(LOG_LEVEL, $error->getErrorMessage(), __FILE__, __LINE__, __CLASS__); 
      return false; 
     } 
     return true; 
    } 

    ... 
    ... 
    ... 
} 

如果我使用簡單Statemetn與標準的選擇查詢，而不是它的作品。

有什麼建議嗎？

Answer 1

您會看到此錯誤，因爲您只能將變量綁定到WHERE子句。準備好的語句機制不僅僅是一個榮耀的字符串格式化程序。它有關於什麼可以綁定以及不能綁定的規則，以及如何在發送給Cassandra時綁定事物以消除任何含糊不清的規則。

你需要去嘗試這樣的：

$statement = $this->session->prepare(
    "SELECT key1, key2, col1, col2 FROM yourKeyspaceName.yourTableName WHERE key1 = ? AND key2 = ?"); 
$results = $this->session->execute($statement, new Cassandra\ExecutionOptions(array(
    'arguments' => array($key1,$key2) 
    )));