From: Richard Huxton <dev@archonet.com>
To: ON.KG <skyer@on.kg>
Cc: pgsql-sql <pgsql-sql@postgresql.org>
Subject: Re: What is faster?
Date: Mon, 06 Jun 2005 17:09:55 +0100
Message-ID: <42A47553.5060408@archonet.com> (raw)
In-Reply-To: <15836788703.20050606210213@on.kg>
References: <OF070A806E.9AC2F48A-ON65257018.003D07AB-65257018.003DF74B@flextronicssoftware.com>
<42A43791.7030306@archonet.com>
<17434586625.20050606202531@on.kg>
<42A4616E.8070101@archonet.com>
<15836788703.20050606210213@on.kg>
ON.KG wrote:
> Hi All!
>
>>>What is faster - SLECTion data from one large table (200 000 - 300 000
>>>records), or SELECTion from a few small tables (example, 2 tables 150
>>>000 records each)?
>
> RH> It depends. Are you selecting all records? One record? A few records? If
> RH> one or a few, do you have a suitable index on the table(s)? Is the table
> RH> clustered? Expected to be cached in RAM?
>
> RH> Do you have a specific problem, or reason to believe you may encounter one?
>
> It's a real problem
>
> For example i have two large tables
> Structure of tables is same - has two fields - id, ip
>
> Now i'm using two selection from each in one transaction
> Each of them selects only one record
> selection clase like WHERE ip = 'xxx.xxx.xxx.xxx'
> so it is searches existance of IP in each table
>
> tables are clustered
OK - so the tables aren't updated frequently, I assume. Do you have an
index on "ip"?
> about cached in RAM - i'm novice in Postgresql - how does it work?
The operating-system will keep frequently used disk-blocks in memory.
You don't have to do anything. Have you done any performance tuning in
your postgresql.conf file? If not, try reading:
http://www.powerpostgresql.com/PerfList> now i need to make much faster as it is possible
> and have an idea just merge two tables in one - will it help me?
If they hold the same information, they probably shouldn't have been
split in the first place.
--
Richard Huxton
Archonet Ltd
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To: pgsql-sql@postgresql.org
Cc: dev@archonet.com, skyer@on.kg
Subject: Re: What is faster?
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