Re: tricky query - Mailing list pgsql-performance

From Sebastian Hennebrueder
Subject Re: tricky query
Date
Msg-id 42C1B55E.40405@laliluna.de
Whole thread Raw
In response to Re: tricky query  (John A Meinel <john@arbash-meinel.com>)
List pgsql-performance
John A Meinel schrieb:

> John A Meinel wrote:
>
>>
>
> Well, I was able to improve it to using appropriate index scans.
> Here is the query:
>
> SELECT t1.id+1 as id_new FROM id_test t1
>    WHERE NOT EXISTS
>        (SELECT t2.id FROM id_test t2 WHERE t2.id = t1.id+1)
>    ORDER BY t1.id LIMIT 1;
>
> I created a test table which has 90k randomly inserted rows. And this is
> what EXPLAIN ANALYZE says:
>
>


As Cosimo stated the result can be wrong. The result is always wrong
when the id with value 1 does not exist.

--
Best Regards / Viele Grüße

Sebastian Hennebrueder

----

http://www.laliluna.de

Tutorials for JSP, JavaServer Faces, Struts, Hibernate and EJB

Get support, education and consulting for these technologies - uncomplicated and cheap.


pgsql-performance by date:

Previous
From: "Merlin Moncure"
Date:
Subject: Re: tricky query
Next
From: Billy extyeightysix
Date:
Subject: optimized counting of web statistics