Hi,
I asked a few days ago how to handled concurrency with Cake. Thanks to
some members of this group, examples and time, I have a possible solution.
However, I need your experience to validate this solution.
I want to warn users when a record they save was modified in the
meanwhile by somebody else.
I add a datetime column in the table called "tst" (I can't use
"modified" column, 'cause the value of this column seems to be updated
before the callback 'beforeSave'... and of course, I use beforeSave
method !).
On the beforeSave(), I start a transaction and lock "for update" the
record. Then I compare the tst value with the value I retrieved. If it's
the same, I go on and update the tst value with the current datetime. If
not, I halt the process with an error.
I must add in my view $form->hidden("model.tst").
I should do the same kind of process on beforeDelete()
If a deadlock or timeout occurs, I handle these errors somewhere else.
Any opinion ? A way to improve it ?
Thanks !
function beforeSave()
{
foreach ($this->data as $key=>$value)
{
if (!isset($value['tst']))
{
continue;
}
$pkValue = $this->id;
$pkCol = $this->primaryKey;
$pkType = $this->getColumnType($this->primaryKey);
$db =& ConnectionManager::getDataSource($this->useDbConfig);
$db->begin($this);
$sql = "SELECT tst FROM " . $this->table . " WHERE " .
$pkCol . " = ";
switch ($pkType) {
case 'integer': // TODO : add other numeric type
break;
default:
$pkValue = "'".$pkValue."'";
break;
}
$sql.=$pkValue. " FOR UPDATE";
$modifiedInDB = $this->query($sql);
if (!count($modifiedInDB))
{
// Record deleted
$this->WWsetSqlErrMsg("Enregistrement déjà supprimé");
$db->rollback($this);
return false;
}
if ($modifiedInDB[0][$this->table]['tst'] != $value['tst'])
{
// Record deleted by somebody else
$this->WWsetSqlErrMsg("Enregistrement modifié par un
autre utilisateur");
$db->rollback($this);
return false;
}
else
{
$this->set('tst',date("Y-m-d G:i:s",strtotime('now')));
}
}
return true;
}
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