Re: Unlogged vs. In-Memory

On Tue, May 3, 2011 at 6:46 PM, Joshua Berkus <josh@agliodbs.com> wrote:
>
> Saying "It's like a in-memory table" is a lot more successful.  And it's using the term "in-memory" the same way a
lotof other DBMSes market it, i.e. in-memory == non-durable & no disk writes. 

Unlogged tables *are* written to disk though. And may be read from
there too - they are not pinned into memory.

> The important thing from my perspective is that unlogged tables give us the capabilities of a lot of the "in-memory"
databases... with unlogged tables and fsync off, for example, PostgreSQL becomes a viable caching database. 
>
> When doing PR, it's more important to use terms people recognize than to use terms which are perfectly accurate.
 Nobodyexpects a news article to be perfectly accurate anyway. 

I consider the term to be pretty much 100% inaccurate. When you say
in-memory to me, I think of a table that is pinned into buffer cache,
as you can do in some DBMS', thus *ensuring* the reads are fast, or of
a database or table that operates entirely in memory (perhaps with
occasional disk writes for persistence) like VoltDB, Redis or MySQL's
Memory storage manager.

> However, I posted this because I think that several folks in the community feel that this is going too far into the
landof marketese, and I want to hash it out and get consensus before we start pitching 9.1 final. 

Thank you.

--
Dave Page
Blog: http://pgsnake.blogspot.com
Twitter: @pgsnake

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