It would be nice to have ON COMMIT triggers for this use.
However you can emulate ON COMMIT triggers with a modification of the
memcache update process :
- A standard trigger sends the data to update to memcache
- The trigger also sends the PID
- Instead of being used immediately, this data is kept in a buffer
- Notify is issued
On commit :
- postgres sends the NOTIFY signal
- the memcache updater reads the NOTIFY (which embeds the PID I believe)
; it finds the buffered data sent above and uses it to update memcached
On rollback :
- Interesting problem ;)))
OK, it's a kludge. When can we get ON COMMIT triggers ?
> On Tue, Apr 04, 2006 at 12:24:42AM -0700, C Storm wrote:
>> I was wondering if anyone on the list has a successful installation of
>> pgmemcache running
>> that uses LISTEN/NOTIFY to signal a successfully completed transaction,
>> i.e., to get around the fact
>> that TRIGGERS are transaction unaware. Or perhaps any other
>> information regarding a successful
>> deployment of pgmemcache.
>
> The problem with attempting that is that you'd have a window between
> transaction commit and when the cache was invalidated. If that's
> acceptable then it shouldn't be too difficult to set something up using
> LISTEN/NOTIFY like you describe.
