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From "Andrzej Bialecki (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3218) Make CFS appendable
Date Fri, 19 Aug 2011 20:55:27 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13087963#comment-13087963
] 

Andrzej Bialecki  commented on LUCENE-3218:
-------------------------------------------

bq. I think append-only filesystems (eg HDFS) can make their own impl that uses the file length
instead (like AppendingCodecc).

AppendingCodec solves only one issue, that of postings and SegmentInfos. I'm worried that
adding seek+rewrite tricks in other places that are not under the control of Codec or under
any other configurable implementation (such as CFS) will ultimately prevent the efficient
use of Lucene on Hadoop. Unless we put those places under the control of a Codec (or some
other configurable interface).

> 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: 4.0
>            Reporter: Simon Willnauer
>            Assignee: Simon Willnauer
>             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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