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Using Zend Framework, I need to (1) read a record from a MySQL database, and (2) immediately write back to that record to indicate that it has been read. I don't want other processes or queries to be able to read from or write to the same record in between steps (1) and (2).

I was considering using a transaction for these steps. If I use the following methods, will that fulfil my requirements?

Zend_Db_Adapter_Abstract::beginTransaction()
Zend_Db_Adapter_Abstract::commit()
Zend_Db_Adapter_Abstract::rollBack()
Luke Eller
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1 Answers1

14

Presupposing you are using the InnoDB engine for tables that you will issue transactions on:

If the requirement is that you first need to read the row and exclusively lock it, before you are going to update it, you should issue a SELECT ... FOR UPDATE query. Something like:

$db->beginTransaction();
try
{
    $select = $db->select()
                 ->forUpdate() // <-- here's the magic
                 ->from(
                     array( 'a' => 'yourTable' ),
                     array( 'your', 'column', 'names' )
                 )
                 ->where( 'someColumn = ?', $whatever );

    $result = $this->_adapter->fetchRow( $select );

    /*
      alter data in $result
      and update if necessary:
    */
    $db->update( 'yourTable', $result, array( 'someColumn = ?' => $whatever ) );

    $db->commit();
}
catch( Exception $e )
{
    $db->rollBack();
}

Or simply issue 'raw' SELECT ... FOR UPDATE and UPDATE SQL statements on $db of course.

Decent Dabbler
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  • The for update is critical. I had a similar situation implementing a queue. Thanks for the tip. – four43 Jan 22 '13 at 21:03
  • Looks like a very similar construction used for Zend framework v.3 also: beginTransaction(), commit(), rollback() functions. – Vaha Feb 21 '19 at 15:37