On Sat, Mar 24, 2012 at 3:22 PM, Joshua Berkus
<josh@agliodbs.com> wrote:
Billy,
> I've done a brief search of the postgresql mail archives, and I've
> noticed a few projects for adding query caches to postgresql, (for
> example, Masanori Yamazaki's query cache proposal for GSOC 2011),
... which was completed, btw. Take a look at the current release of pgPool.
Are you proposing this for GSOC2012, or is this just a general idea?
just a general idea, but if someone wants to work on it for GSOC2012, I wouldn't mind giving a helping hand. I'm not a student, so GSOC probably doesn't apply to me.
> I'm wondering if anyone would be interested in a query cache as a
> backend to postgresql? I've been playing around with the postgresql
> code, and if I'm understanding the code, I believe this is possible.
Well, you'd have to start by demonstrating the benefit of it. The advantage of query caches in proxies and clients is well-known, because you can offload some of the work of the database onto other servers, this increasing capacity. Adding a query cache to the database server would require the "query identity recognition" of the cache to be far cheaper (as in 10X cheaper) than planning and running the query, which seems unlikely at best.
I figured I'd create the md5 digest of the sourceText of a query, and then look that up in a hash. I don't think that will be very expensive. I'll have another hash to keep track of which queries are dependent on which relations, so that when a relation is changed somehow (and committed), the query is then invalidated and removed from the query hash.
Billy