Date: Thu, 29 Jan 2015 12:42:12 -0700 (MST)
From: David G Johnston <david.g.johnston@gmail.com>
To: pgsql-admin@postgresql.org
Message-ID: <1422560532253-5836010.post@n5.nabble.com>
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Subject: Re: Space taken by Null values
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Basant Dagar wrote
> Gurus--
>=20
> I have big flat table with 100 columns in it. For about 40% of its data,
> 90
> columns would be null out of 100.And  this table keeps growing and will
> initial have more than 100 million rows.
>=20
> =E2=80=8BMay I know, will this impact the size in  anyways as I heard nul=
ls will
> take no or very little space in PostgreSQL unlike oracle. even for
> millions
> of rows with many columns in it. Is that true?
>=20
>=20
> =E2=80=8BAnd if that is not true, would you recommend to make this table =
into 2
> tables with the 2nd table containing those =E2=80=8B40% records with only=
 10
> required columns in it?

IIRC a single null occupies one bit.

I would indeed expect to be able to create two tables and minimize or
eliminate the number of columns defined to allow NULL.  If that is what you
are thinking (your question is unclear on this point) then go ahead; keeping
mind that I obviously have no clue what any of those 100 columns is...

David J.


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