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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4053) Reduce metadata cache file size
Date Sat, 14 Nov 2015 00:52:11 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15004989#comment-15004989
] 

ASF GitHub Bot commented on DRILL-4053:
---------------------------------------

Github user parthchandra commented on the pull request:

    https://github.com/apache/drill/pull/254#issuecomment-156601055
  
    I used an alternate cache file because the code is simplistic and uses Jackson deserialization
which essentially means that one needs to know the version of the file before one reads it.
Right now I also ignore the older metadata cache file and remove it if refresh metadata is
called.
    I could maintain multiple versions and dispatch on version, though I would still prefer
to keep the version info in the file name. 
    Let me know if you think that is necessary.


> Reduce metadata cache file size
> -------------------------------
>
>                 Key: DRILL-4053
>                 URL: https://issues.apache.org/jira/browse/DRILL-4053
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Metadata
>    Affects Versions: 1.3.0
>            Reporter: Parth Chandra
>            Assignee: Parth Chandra
>             Fix For: 1.4.0
>
>
> The parquet metadata cache file has fair amount of redundant metadata that causes the
size of the cache file to bloat. Two things that we can reduce are :
> 1) Schema is repeated for every row group. We can keep a merged schema (similar to what
was discussed for insert into functionality) 2) The max and min value in the stats are used
for partition pruning when the values are the same. We can keep the maxValue only and that
too only if it is the same as the minValue.



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