On Nov 6, 2011, at 9:03 AM, Wei-Ning Huang wrote:
>
> Can I ask you more about the queue operations you talked about?
> currently I'm using like this:
>
> results = db.query(Table).filter(condition & (Table.status !=
> 'QUEUED')).with_lockmode('update')
> ids = [result.id for result in results]
> db.query(Table).filter(Table.id.in_(ids)).delete()
> return results
>
> if this correct? I'm not sure if I can delete the rows selected with lockmode
> 'update'.
> Thanks for answering!
right...I usually just do an UPDATE, then when the job completes it's updated
again as COMPLETED. The rows remain in the database as a record of the job
proceeding. A periodic task can delete those rows that are in
COMPLETED/FAILED status which are older than X days.
Alternatively, the job itself can DELETE its own row later. The key is to
emit an UPDATE first so that the status flag prevents the rows from being
grabbed by another process.
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