select * from pg_class;
or
select relname, relpages from pg_class where relname = '[index-name]';
the pages give you the information about the space the index uses, a
page has 8kb.
[...]Every table and index is stored as an array of pages of a fixed
size (usually 8Kb, although a different page size can be selected when
compiling the server). In a table, all the pages are logically
equivalent, so a particular item (row) can be stored in any page. In
indexes, the first page is generally reserved as a metapage holding
control information, and there may be different types of pages within
the index, depending on the index access method. [...]
Source-URL:
http://www.postgresql.org/docs/8.0/interactive/storage-page-layout.html
jose fuenmayor wrote:
> ---------- Forwarded message ----------
> From: jose fuenmayor <jafn82@gmail.com>
> Date: Aug 22, 2005 1:37 PM
> Subject: Indexes (Disk space)
> To: pgsql-admin@postgresql.org
>
>
> Hi all,
> I have the following question.
> Is there anyway for me to know how much space on disk will ocupy an
> index, created in a determined row or rows of a table?, anything like
> a rule, formula, calculation? that allow me to know in advance how
> much space will the index use before actually created it.
>
> I aprecciate all the help you can give me
>
> Thanks in advance.
>
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