Re: Postgres as In-Memory Database?

Em 17/11/2013 20:46, Andreas Brandl escreveu:
> 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
>
>
Worndeful, never knew about it.
I'm ready ASAP.

Regards

Edson