Re: Fwd: Indexes (Disk space)

Ok I understand but I need to know the size of the index before i create it
I need to know how much space it will ocupy (before actually create
the index, having the information of the table on wich I will build
the index), is this possible?
thanks in advance to everyone that can help me.

On 8/23/05, Aldor <an(at)mediaroot(dot)de> wrote:
> 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(at)gmail(dot)com>
> > Date: Aug 22, 2005 1:37 PM
> > Subject: Indexes (Disk space)
> > To: pgsql-admin(at)postgresql(dot)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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