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@xxxxxxxxxxxxxx [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of Tom Lane Sent: Wednesday, November 07, 2007 12:05 PM To: Ron Johnson Cc: pgsql-general@xxxxxxxxxxxxxx Subject: Re: DB on a ramdisk (was Re: Temporary, In-memory Postgres DB?) Ron Johnson <ron.l.johnson@xxxxxxx> 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. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
