INSERT and UPDATE the same row in the same TRANSACTION? (MySQL) - mysql

Question

So here's my problem:
I have an article submission form with an optional image upload field.
When the user submits the form - this is roughly what happens:
if($this->view->form->isValid($_POST){
$db->beginTransaction();
try{
// save content of POST to Article table
if(!$this->_saveArticle($_POST)){
return;
}
// resize and save image using ID generated by previous condition
if(!$this->_saveImage($_FILES){
$db->rollback();
return;
}
// update record if image successfully generated
if(!$this->_updateArticle(){
$db->rollback();
}
$db->commit();
}
}catch (Exception $e){
$db->rollback()
}
All Models are saved using mappers, which automate "UPSERT" functionality by checking for the existence of a surrogate key
public function save($Model){
if(!is_null($Model->id_article){
$Mapper->insert($Model->getFields());
return;
}
$Mapper->update($Model->getFields(),$Model->getIdentity());
}
The article table has a composite UNIQUE index of ID,Title and URL. In addition, I'm generating a UID that gets added to the ID field of the Model prior to insert (instead of auto-incrementing)
When I try to execute this, it runs fine for the first article inserted into the table - but subsequent calls (with radically different input) triggers a DUPLICATE KEY error. MySQL throws back the ID generated in condition 1 (_saveArticle) and complains that the key already exists...
I've dumped out the Model fields (and the condition state - i.e. insert | update) and they proceed as expected (pseudo):
inserting!
id = null
title = something
content = something
image = null
updating!
id = 1234123412341234
title = something
content = something else
image = 1234123412341234.jpg
This row data is not present in the database.
I figure this could be one of a few things:
1: I'm loading a secondary DB adapter on user login, allowing them to interface with several sites from one login - this might be confusing the transaction somehow
2: It's a bug of some description in the Zend transaction implementation (possibly triggered by 1)
3: I need to replace the save() with an INSERT ... ON DUPLICATE
4: I should restructure the submission process, or generate a name for the image that isn't dependent on the UID of the previously inserted row.
Still hunting, but I was wondering if anyone else has encountered this kind of issue or could point me in the direction of a solution
best SWK

Answer 1

OK - just for the record, this is entirely possible. The problem was in my application architecture. I was catching Exceptions in my Mapper classes that were handling persistence - and then querying them to return boolean states and thus interrupt the process. This was in turn breaking the try/catch loop which was preventing the insert/update from working correctly.
To summarise - Yes - you CAN insert and update the same row in a single transaction. I've ticked community wiki to cancel rep out