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From: "Uwe Schindler" <uwe@thetaphi.de>
To: <java-user@lucene.apache.org>
References: <393CE17D-24A9-4E99-A214-BBA004F85B24@bammers.net>
In-Reply-To: <393CE17D-24A9-4E99-A214-BBA004F85B24@bammers.net>
Subject: RE: Index size variation 
Date: Fri, 3 Mar 2017 19:37:42 +0100
Message-ID: <000801d2944d$3ed75de0$bc8619a0$@thetaphi.de>
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archived-at: Fri, 03 Mar 2017 18:37:52 -0000

Hi Chris,

as always: "it depends". Generally I would reserve space of =
approximately the "original" index size. Most indexes that are =
continuously updated have an overhead by 40% for deleted documents. The =
remaining 60% are indeed used for merging. Please also keep in mind that =
if IndexReaders are open while merging, you may see not all used disk =
space from the directory listing, because some files that were merged =
but are still open in IndexReaders already disappeared from directory =
listing (deleted during merge), but still consume disk space (delete on =
last close POSIX semantics).

If you also "forceMerge" your index (you should never ever do this), you =
may temporarily need 3 times the index size.

Uwe

-----
Uwe Schindler
Achterdiek 19, D-28357 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de

> -----Original Message-----
> From: Chris Bamford [mailto:chris@bammers.net]
> Sent: Friday, March 3, 2017 7:24 PM
> To: java-user@lucene.apache.org
> Subject: Index size variation
>=20
> Hello
>=20
> I have observed that sometimes my index size temporarily increases by =
a
> large amount, presumably while it it merges segments.
>=20
> Is there some documentation on this subject? I am trying to estimate =
total
> disk space I'll need for a project.
>=20
> Thanks
>=20
> Chris
>=20
>=20
>=20
>=20
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