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From "Michael McCandless (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3218) Make CFS appendable
Date Sat, 20 Aug 2011 16:07:27 GMT


Michael McCandless commented on LUCENE-3218:

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


Generally if we add a cool optimization and it turns out that optimization risks even just
apparent index corruption and/or adds scary traps / confusing complexity to the API I think
we should pull the change and iterate on the issue / branch until these problems are addressed?

We had a similar experience with copyBytes, but that time it was real corruption.

Optimizations aren't worth such risks I think, especially if it's only an index-time opto?

> Make CFS appendable  
> ---------------------
>                 Key: LUCENE-3218
>                 URL:
>             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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