size of a table on postgresql

aravind chandu wrote:

Hello,

The following is the procedure to calculate the disk space
occupied by postgresql from a flat file.

In this I didn't understood some terms

24 bytes: each row header (approximate)
24 bytes: one int field and one text field
+ 4 bytes: pointer on page to tuple

here row header is taken as 24 bytes and in some sites it is given
row header as 40 bytes and in some 32 bytes
http://www.sbras.ru/rus/docs/db/postgres/doc/howto/faq-english.shtml#3.6
http://www.softlab.ntua.gr/facilities/documentation/unix/postgres/faq-english.html

Is the row header value is constant or it is variable?If so what could be the maximun value?
what is that additional +4bytes as pointer on page to tuple.

Should all these were fixed or is there any command to find the values for these fields?

Maybe you want:

http://www.postgresql.org/docs/8.3/interactive/functions-admin.html

pg_relation_size(text) Disk space used by the table or index with the
specified name. The table name can be qualified with a schema name

pg_total_relation_size(text) Total disk space used by the table with the
specified name, including indexes and toasted data. The table name can
be qualified with a schema name

?

Cheers
Tino