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Re: Subquery WHERE IN or WHERE EXISTS faster?

From: Rusty Conover <rconover(at)infogears(dot)com>
To: Ulrich <ulrich(dot)mierendorff(at)gmx(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Subquery WHERE IN or WHERE EXISTS faster?
Date: 2008-06-30 07:44:45
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Jun 30, 2008, at 1:29 AM, Ulrich wrote:

> I think it will be fast, because the "IN set", which is the result  
> of "SELECT processorid FROM users_processors WHERE userid=4040", is  
> limited to a maximum of ~500 processors which is not very big.  
> Increasing Postgres' RAM would be difficult for me, because I am  
> only running a very small server with 256MB RAM and the webserver  
> also likes to use some RAM.
> Does Postgre cache the HASH-Table for later use? For example when  
> the user reloads the website.

No the hash table only lives as long as the query is being executed.   
If you're looking for generic caching, I'd suggest memcached may be  
able to fill your needs.


Rusty Conover
InfoGears Inc.

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Subject: Re: Planner should use index on a LIKE 'foo%' query
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