Re: SELECT TOP %d PERCENT, or SELECT ... LIMIT %d PERCENT ? - Mailing list pgsql-hackers

From Grzegorz Jaskiewicz
Subject Re: SELECT TOP %d PERCENT, or SELECT ... LIMIT %d PERCENT ?
Date
Msg-id B119A552-BB7C-4FE9-8EDE-7D4884BC603D@pointblue.com.pl
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In response to Re: SELECT TOP %d PERCENT, or SELECT ... LIMIT %d PERCENT ?  ("Hitoshi Harada" <umi.tanuki@gmail.com>)
Responses Re: SELECT TOP %d PERCENT, or SELECT ... LIMIT %d PERCENT ?
List pgsql-hackers
that's a shame.
I figure, with the "WITH ... AS .." you can kind of speed up counts,  
just by doing it once - now. But still, it would be great to be able  
to use PERCENT, against estimate.
After all, imagine a table FOO with 5 rows, and something like this:

WITH c AS (select count(*)/4 as n from FOO) select * from FOO limit  
(select n from c) offset (select n*X from c);

now X is for every 25%, but you wan't get to see last row if you use  
offset 75 percent (X=3). Which kind of puts me off the idea of using  
PERCENT anyway, because it isn't quite accurate.

So thanks for answer, I'll pass on this one. Hopefully there would be  
another chance for me to write some patch in future.

ta.


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