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LIMIT clause and long timings

From: Andrea <andrea(dot)b73(at)email(dot)it>
To: pgsql-novice(at)postgresql(dot)org
Subject: LIMIT clause and long timings
Date: 2006-03-28 12:21:37
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
Thank very much for answers to my preceding question. I have obtained a 
plain CSV file from MySQL and I have loaded my PostgreSQL table with 
this file using the COPY command.

I have another question. Now I have a table in PostgreSQL with about 
35000 records. The table has the following fields (sorry, names are in 
   abi char(5) NOT NULL,
   cab char(5) NOT NULL,
   banca char(80) NOT NULL,
   filiale char(60) NOT NULL,
   indirizzo char(80) NOT NULL,
   citta char(40) NOT NULL,
   cap char(16) NOT NULL,
There is a primary key ('abi','cab') and an index for field 'banca'.
This table contains the list of all italian banks.

Note, I have the same table also on MySQL because my intention is to 
test and understand better some SELECT benchmarks using both databases.

On PostgreSQL I have tried:
(10 rows)

Time: 10,000 ms

Then I have tried:
SELECT * FROM banche ORDER BY banca LIMIT 10 OFFSET 34000;
(10 rows)

Time: 2433,000 ms

Why do I get this big timing??? I got similar timings also with MySQL. I 
can think (or better I suppose) a database, in this situation, has to do 
several filterings and seekings to reach the request offset. Is my 
'intuition' correct?

My final target is to create a graphical Java application which uses 
databases using JDBC. I would like, for example, to use a JTable to show 
a database table in a tabular form.
With this (long) timings I can't obtain good performances! Especially 
when I am at the bottom of the table.

What do you think? Is my approach correct??


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Subject: Re: Transfer from MySQL to PostgreSQL
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Subject: Re: delete from joined tables

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