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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4936) docvalues date compression
Date Fri, 19 Apr 2013 15:53:16 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13636508#comment-13636508
] 

Robert Muir commented on LUCENE-4936:
-------------------------------------

First thing that sticks out is maybe to remove the extra pass? Even though it just pulls
the first value...

For the DiskDV codec i feel its simple, just remove the loop and look for 'count == 0'.
For Lucene42, its probably best to just add 'count' for the same reason?

But if it makes things more confusing, maybe just leave it the way it is. Its a little tricky
either way :)
                
> docvalues date compression
> --------------------------
>
>                 Key: LUCENE-4936
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4936
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: core/index
>            Reporter: Robert Muir
>            Assignee: Adrien Grand
>             Fix For: 4.4
>
>         Attachments: LUCENE-4936.patch, LUCENE-4936.patch, LUCENE-4936.patch, LUCENE-4936.patch
>
>
> DocValues fields can be very wasteful if you are storing dates (like solr's TrieDateField
does if you enable docvalues) and don't actually need all the precision: e.g. "date-only"
fields like date of birth with no time component, time fields without milliseconds precision,
and so on.
> Ideally we'd compute GCD of all the values to save space (numberOfTrailingZeros is not
really enough here), but i think we should at least look for values like 86400000, 3600000,
and 1000 to be practical.

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