Re: Problem with estimating pages for a table
| От | Dimitri Fontaine |
|---|---|
| Тема | Re: Problem with estimating pages for a table |
| Дата | |
| Msg-id | 87octw9dm3.fsf@hi-media-techno.com обсуждение исходный текст |
| Ответ на | Problem with estimating pages for a table (Cristina M <cristina.maier@yahoo.com>) |
| Список | pgsql-hackers |
Hi,
Cristina M <cristina.maier@yahoo.com> writes:
> For each varchar column - I add an extra 4 bytes
> For each numeric column - I add an extra 8 bytes
> Add a 28 bytes row overhead.
>
> For example if i have a table with col1: integer, col2: varchar, col3 varchar, I will get:
> pages = (col1width + col2width + 4 + col3width + 4 + 28)* no. of rows
> / block size
You may find Greg Startk's presentation on the topic helpful:
http://wiki.postgresql.org/wiki/Image:How_Long_Is_a_String.pdf
Regards,
--
dim
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