Re: Using window functions to get the unpaginated count for paginated queries

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От Igor Romanchenko
Тема Re: Using window functions to get the unpaginated count for paginated queries
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Msg-id CAP95Gqne4MqA2=Pj4MdBzj0p2iJV+TfHxCfp7jcu4-ks4oauTg@mail.gmail.com
обсуждение исходный текст
Ответ на Re: Using window functions to get the unpaginated count for paginated queries  ("Albe Laurenz" <laurenz.albe@wien.gv.at>)
Ответы Re: Using window functions to get the unpaginated count for paginated queries  (Clemens Park <clemens.park@gmail.com>)
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1) Are there any adverse effects that the above window function can have?

It can cause severe performance degradation, as mentioned before.

2) Are there any cases where the count would return incorrectly?
 
It could return incorrect result if there are some rows with  table.id = NULL . count(table_field) returns the number of rows, where table_field is not NULL.

3) In general, is this an appropriate use-case for using window functions?

It does the job => it is an appropriate use-case for using window functions.


If this query causes performance degradation and you do not need the exact count of rows, it is better to use something from http://wiki.postgresql.org/wiki/Count_estimate or google for "fast postgresql count".

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