Re: DB on a ramdisk (was Re: Temporary, In-memory Postgres DB?) - Mailing list pgsql-general

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Undo an initdb?  Probably the same way you undo unlinking an SQLite
database.

Maybe being wrapped in my own little niche I just don't know enough
about the wide world of hyperfeaturitis, but making "temporary DB"
as a feature seems a little vague.

It doesn't really take that long to create a new database
(especially if it's scripted!), and it's even faster if you make the
"temporary DB" a schema off a public database.

On 11/07/07 11:27, Gauthier, Dave wrote:
> I understand caching.
>
> Here's the reason I'm inquiring into this line of thought...
>
> I already have a "big" on-disk DB with lots and lots of data, and lots
> of stored functions and a data model that works with DB loaders and
> other code that queries out data.  I also have users that want all of
> that, except for the particular data content.  They basically want to
> load a DB with data that's in their scratch area without polluting
> what's in the "main" DB. The cardinality of this "personal, scratch
> data" will be orders of magnitude smaller than what's in the main (could
> all fit in memory).  And once loaded,  they would be able to run all the
> same DB load and query tools that work on the main DB, just redirect to
> the small, personal DB.
>
> This would be a good app for SQLite, but SQLite can't do a lot of the
> things that are running in the main DB (like stored procedures).
>
> It's become clear that PG cannot do a pure in-memory DB like SQLite.
> It's why I initially called this a "longshot" and the answer to my
> question is probably "no".  But enabling something like a pure in-memory
> (and temporary) DB for small apps that can reap all the wonderful
> features of PG would make it very attractive for some users.  Just
> something to think about for future development.
>
> One question I had earlier that I don't think got answered was how to
> undo an "initdb".  "dropdb" drops a DB, but how do I undo an "initdb"?
>
>
> -dave
>
>
>
>
> -----Original Message-----
> From: pgsql-general-owner@postgresql.org
> [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Tom Lane
> Sent: Wednesday, November 07, 2007 12:05 PM
> To: Ron Johnson
> Cc: pgsql-general@postgresql.org
> Subject: Re: DB on a ramdisk (was Re: [GENERAL] Temporary, In-memory
> Postgres DB?)
>
> Ron Johnson <ron.l.johnson@cox.net> writes:
>> On 11/07/07 09:58, Tom Lane wrote:
>>> Or put it on a ramdisk filesystem.
>
>> But doesn't that just add more overhead and reduce the amount of
>> memory that the OS can cache things in?
>
> It's very possibly not a win, but the kinds of people who ask this
> question at all do not understand the concept of caching, so I'm
> sure they'll be happier with a solution where the data demonstrably
> never hits disk ;-)
>
> A case where it could be a win is where you are thrashing the DB with
> heavy update load.  Even if everything is cached there will be a pretty
> serious amount of disk write traffic, which'd possibly interfere with
> other system activity.

- --
Ron Johnson, Jr.
Jefferson LA  USA

Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!

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