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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3218) Make CFS appendable
Date Mon, 22 Aug 2011 17:13:29 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088826#comment-13088826
] 

Uwe Schindler commented on LUCENE-3218:
---------------------------------------

Hi Simon,

thanks for taking care. This looks really nice and easier to understand. I agree, the problem
with the RAF open file is hard to manage (especially when to close it).

One small suggestion: Currently the CFS file is opened twice: One time to read the contents
and a second time to read the actual files using the handle (and for new format to read the
CFE file, but thats unavoidable - once we nuke old index support in Lucene 5, we can always
open the cfe first and read the contents, but until then we need to do both). Why not open
the IndexInputHandle at the beginning and then simply request a full slice for the directory
initialization (or ideally only that part that contains the directory)? The slice can then
be closed afterwards as before.

So very cool work!
Greetings from Berkeley!

> Make CFS appendable  
> ---------------------
>
>                 Key: LUCENE-3218
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3218
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/index
>    Affects Versions: 3.4, 4.0
>            Reporter: Simon Willnauer
>            Priority: Blocker
>             Fix For: 3.4, 4.0
>
>         Attachments: LUCENE-3218.patch, LUCENE-3218.patch, LUCENE-3218.patch, LUCENE-3218.patch,
LUCENE-3218.patch, LUCENE-3218_3x.patch, LUCENE-3218_test_fix.patch, LUCENE-3218_tests.patch
>
>
> Currently CFS is created once all files are written during a flush / merge. Once on disk
the files are copied into the CFS format which is basically a unnecessary for some of the
files. We can at any time write at least one file directly into the CFS which can save a reasonable
amount of IO. For instance stored fields could be written directly during indexing and during
a Codec Flush one of the written files can be appended directly. This optimization is a nice
sideeffect for lucene indexing itself but more important for DocValues and LUCENE-3216 we
could transparently pack per field files into a single file only for docvalues without changing
any code once LUCENE-3216 is resolved.

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