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From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3218) Make CFS appendable
Date Sun, 21 Aug 2011 06:13:27 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088321#comment-13088321
] 

Simon Willnauer commented on LUCENE-3218:
-----------------------------------------

bq. I think we should back out these CFS changes for now.

-1 

I think we are over reacting here, especially robert gets too crazy about this. Honestly I
think CFS should be detached from directory and we should make it a delegating directory if
at all. That way we would always operate on the right directory, can safely create two files
and keep Directory itself clean. We can still add the ability to partially map a certain file
(offset, length) into memory like we do now in the specialized CFS Dirs. This entire think
is not a problem of appending at all IMO. 

how does that sound? I think this would solve all the problems we are having and keeps it
appendable.

simon

> 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
>            Assignee: 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_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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