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Hi Nathan,<br>
<br>
I think thats simply up to the application how this is handled.<br>
E.g. you could just "delete" or "update" the cached variable at the
place where the data in the table is changed, thats<br>
how we handle it in most areas.<br>
Or you use some "version" which increases if the data changed and use
that version-number together with the key to retrieve<br>
data from memcached.<br>
<br>
<br>
thomas<br>
<br>
Nathan Nobbe schrieb:
<blockquote
cite="mid:7dd2dc0b0705210705q57b7ccdag1302251325293bca@mail.gmail.com"
type="cite">All,<br>
<br>
I recently began investigating memcached, and im very excited about
it. im planning on using it w/ php to implement variables whose
lifetime can be the duration of the application.<br>
I understand that storing the results of queries to the database can
increase efficiency if those variables are checked for the data first
on consecutive requests for the data they store, but
<br>
i still have a disconnect...<br>
what i dont understand is when the data profile of a particular table
changes, and the variable in the memcache that represents that table
becomes stale, how can the variable be updated efficiently?
<br>
obviously w/ php and a unix system, a simple cron could be used to
poll the database periodically to see if there are changes to the data
profile of a given table. i was thinking to make this even more<br>
efficient; triggers could be employed (im using mysql 5+) to update a
table, call it <span style="font-style: italic;">recent_tables_that_changed</span>,
dedicated to signifying particular tables in the database have
changed. then the cron'd php script could simply check <span
style="font-style: italic;">
recent_tables_that_changed </span>to determine which, if any,
application variables had become stale (do to a change in data
profile). the stale variable could then be updated and the record
removed from <span style="font-style: italic;">
recent_tables_that_changed</span>.<br>
though decent, i am personally not a fan of this approach, because
there would still be a frequent query running against the database just
to determine what data had changed so that application variables in the
cache
<br>
would not remain stale for long once theyve become stale.
additionally, the mechanisms' responsiveness would be limited to the
time granularity of cron, which i believe is a minute. im wondering if
there is some way to signal the cache only when tables, represented by
application variables, have changed. if you dont feel like typing out
a response, because this is probably a naive question, would anyone
mind directing me to a resource or two where i could read up on the
topic myself?
<br>
<br>
(sorry for the lengthy posting)<br>
thanks,<br>
<br>
-Nathan<br>
</blockquote>
<br>
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