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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (LUCENE-4512) Additional memory savings in CompressingStoredFieldsIndex.MEMORY_CHUNK
Date Tue, 30 Oct 2012 17:52:12 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-4512?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Adrien Grand updated LUCENE-4512:
---------------------------------

    Attachment: LUCENE-4512.patch

Patch. I removed {{MEMORY_DOC}} and modified {{MEMORY_CHUNK}} to apply the proposed changes:
 - it works with blocks of n=1024 (hard-wired) chunks,
 - for every block, doc bases and start pointers are compressed by only storing the delta
from the average.
                
> Additional memory savings in CompressingStoredFieldsIndex.MEMORY_CHUNK
> ----------------------------------------------------------------------
>
>                 Key: LUCENE-4512
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4512
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Adrien Grand
>            Assignee: Adrien Grand
>            Priority: Minor
>             Fix For: 4.1
>
>         Attachments: LUCENE-4512.patch
>
>
> Robert had a great idea to save memory with {{CompressingStoredFieldsIndex.MEMORY_CHUNK}}:
instead of storing the absolute start pointers we could compute the mean number of bytes per
chunk of documents and only store the delta between the actual value and the expected value
(avgChunkBytes * chunkNumber).
> By applying this idea to every n(=1024?) chunks, we would even:
>  - make sure to never hit the worst case (delta ~= maxStartPointer)
>  - reduce memory usage at indexing time.

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