Re: Postgres as In-Memory Database?

Edson,

> Em 17/11/2013 19:26, Stefan Keller escreveu:
> > Hi Edson
> >
> > As Rob wrote: Having a feature like an in-memory table like SQLite
> > has
> > [1] would make application cahces obsoleteand interesting to
> > discuss
> > (but that was'nt exactly what I asked above).
>
> Hi, Stephan,
>
> I don't think any feature you add to database server would bring
> obsolescence to app server caches: app server caches have just no lag
> at
> all:
>
> 1) Don't need network connection to database server
> 2) Don't need to materialize results (for instance, I have in mind a
> Java or .Net app server running hundred thousands of objects in
> memory).
>
> IMHO, no matter how much you improve database, app server caches
> provides additional level of speed that cannot be achieved by
> database.
>
> That said, I still can see huge improvements in database server.
> Having strong in memory operation would bring substantial
> improvements.
> For instance, if you have in-memory database (tables, indexes, etc)
> for
> all sort of queries, and just **commit** to disks, then you will have
> unprecedent performance.
> I would get benefit from this architecture, since typical customer
> database has < 64Gb on size (after 2 or 3 years of data recording).
> So,
> a database server with 64Gb of memory would keep everything in
> memory,
> and just commit data to disc.
>
> In this case, commited data would be instantly available to queries
> (because they are all in memory) while log (changes) is recorded in a
> fast disk (a SSD, perhaps) and then those changes are made persistent
> data, written async into slow massive disks (SCSI or SAS).
>
> This would allow also a hybrid operation (too keep as much data pages
> as
> possible in memory, with a target of 50% or more in memory).
>
> When database server is started, it would have lazy load (data is
> loaded
> and kept in memory as it is used) or eager load (for slower startup
> but
> faster execution).

not sure I fully understand your point. Isn't this the typical mode-of-operation plus added cache warming?

Anyways, just wanted to point you to [1] which gives a good overview of cache warming techniques.

Regards,
Andreas

[1] http://raghavt.blogspot.fr/2012/04/caching-in-postgresql.html