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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4123) Add CachingRAMDirectory
Date Sat, 30 Jun 2012 08:39:43 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13404429#comment-13404429
] 

Uwe Schindler commented on LUCENE-4123:
---------------------------------------

You should make the II correctly throw IOExceptions like MMap does, so catch the AIOOBE and
rethrow as EOFException (just copy the code). This does not have any speed effect. Otherwise
some tests will definitely fail.
                
> Add CachingRAMDirectory
> -----------------------
>
>                 Key: LUCENE-4123
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4123
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: core/store
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>         Attachments: LUCENE-4123.patch
>
>
> The directory is very simple and useful if you have an index that you
> know fully fits into available RAM.  You could also use FileSwitchDir if
> you want to leave some files (eg stored fields or term vectors) on disk.
> It wraps any other Directory and delegates all writing (IndexOutput) to
> it, but for reading (IndexInput), it allocates a single byte[] and fully
> reads the file in and then serves requests off that single byte[].  It's
> more GC friendly than RAMDir since it only allocates a single array per
> file.
> It has a few nocommits still, but all tests pass if I wrap the delegate
> inside MockDirectoryWrapper using this.
> I tested with 1M Wikipedia english index (would like to test w/ 10M docs
> but I don't have enough RAM...); it seems to give a nice speedup:
> {noformat}
>                 Task    QPS base StdDev base  QPS cachedStdDev cached      Pct diff
>              Respell      197.00        7.27      203.19        8.17   -4% -   11%
>             PKLookup      121.12        2.80      125.46        3.20   -1% -    8%
>               Fuzzy2       66.62        2.62       69.91        2.85   -3% -   13%
>               Fuzzy1      206.20        6.47      222.21        6.52    1% -   14%
>        TermGroup100K      160.14        6.62      175.71        3.79    3% -   16%
>               Phrase       34.85        0.40       38.75        0.61    8% -   14%
>       TermBGroup100K      363.75       15.74      406.98       13.23    3% -   20%
>             SpanNear       53.08        1.11       59.53        2.94    4% -   20%
>     TermBGroup100K1P      222.53        9.78      252.86        5.96    6% -   21%
>         SloppyPhrase       70.36        2.05       79.95        4.48    4% -   23%
>             Wildcard      238.10        4.29      272.78        4.97   10% -   18%
>            OrHighMed      123.49        4.85      149.32        4.66   12% -   29%
>              Prefix3      288.46        8.10      350.40        5.38   16% -   26%
>           OrHighHigh       76.46        3.27       93.13        2.96   13% -   31%
>               IntNRQ       92.25        2.12      113.47        5.74   14% -   32%
>                 Term      757.12       39.03      958.62       22.68   17% -   36%
>          AndHighHigh      103.03        4.48      133.89        3.76   21% -   39%
>           AndHighMed      376.36       16.58      493.99       10.00   23% -   40%
> {noformat}

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