Thread: cacheing metadata

cacheing metadata

From
Dave Cramer
Date:
There is some interest in caching meta-data. I am wondering what the
community thinks of the idea.

Notionally it would be used to speed up DataBaseMetaData queries. It
will require some work on the backend to create triggers on schema
changes. This is being considered as we speak.

The one challenge is that we don't have non-blocking sockets so we
basically have to do an empty query to see if the cache is dirty and
then reload it if it is

Kris has already commented that this sounds like a fair bit of
complexity for a method that is rarely called.

Dave

--
Dave Cramer
519 939 0336
ICQ # 14675561


Re: cacheing metadata

From
Oliver Jowett
Date:
Dave Cramer wrote:
> There is some interest in caching meta-data. I am wondering what the
> community thinks of the idea.

Are there really metadata-query-heavy apps out there that would benefit?
  Do you have an example of one? I'd have thought that most if not all
of the metadata-related tables would all be sitting in cache anyway.

It seems like this is a special case of the more general "I run
expensive queries and don't want to rerun them to pick up changes". And
a very special case at that -- metadata doesn't usually change very often.

If the app is essentially a UI frontend I'd say you could get away with
caching results in the app (not the driver) and having a "reload" button.

If the app really needs up-to-the-moment metadata state to control
whatever actions that follow, it'll need to hit the DB with the full
metadata query while in a transaction to get the right isolation
characteristics, won't it?

> Notionally it would be used to speed up DataBaseMetaData queries. It
> will require some work on the backend to create triggers on schema
> changes. This is being considered as we speak.

If you're going to be adding support triggers to every DB anyway, why
not bite the bullet and do a stored proc that maintains a cache table of
materialized metadata, or something similar?

-O

Re: cacheing metadata

From
Oliver Jowett
Date:
Oliver Jowett wrote:
> Dave Cramer wrote:
>
>> There is some interest in caching meta-data. I am wondering what the
>> community thinks of the idea.

Urgh -- getting email repeats from february again. Sorry.

-O