Hi Kirk,
Kirk Ouimet wrote:
Hi List,
I am currently storing an object in a MySQL database. The object is
continually being updated by many (possibly simultaneous) requests. Workflow
looks something like this:
1. Data comes in from one of many sources
2. PHP reads the object from the database
3. PHP adds data to the object
4. PHP writes the object back to the database
I think I'm running into a concurrency issue where I have record of new data
being received, but the database object does not reflect the new data. I
feel like I need to make the object a mutex but I have no idea how to go
about doing that with PHP. Can anyone provide alternative designs that will
be a little more robust and handle concurrency?
Try wrapping the select and the update in one transaction. And doing a
SELECT ... FOR UPDATE:
$pdo->beginTransaction();
$stmt = $pdo->query("SELECT obj FROM table_with_object WHERE object_id =
1 FOR UPDATE");
// ...
// get the object out of the statement and have php add the data to it
// ...
$pdo->exec("UPDATE table_with_object SET object = '$obj' WHERE object_id
= 1");
$pdo->commit();
This is just a guess, i haven't tested it. Also make sure you use
prepared statements to prevent SQL injection, I didn't here for the sake
of brevity.
Alvaro
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