[jira] [Created] (HIVE-6157) Fetching column stats slower than the 101 during rush hour

["Gunther Hagleitner (JIRA)" <ji...@apache.org>]

Gunther Hagleitner created HIVE-6157:
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             Summary: Fetching column stats slower than the 101 during rush hour
                 Key: HIVE-6157
                 URL: https://issues.apache.org/jira/browse/HIVE-6157
             Project: Hive
          Issue Type: Bug
    Affects Versions: 0.13.0
            Reporter: Gunther Hagleitner


"hive.stats.fetch.column.stats" controls whether the column stats for a table are fetched during explain (in Tez: during query planning). On my setup (1 table 4000 partitions, 24 columns) the time spent in semantic analyze goes from ~1 second to ~66 seconds when turning the flag on. 65 seconds spent fetching column stats...

The reason is probably that the APIs force you to make separate metastore calls for each column in each partition. That's probably the first thing that has to change. The question is if in addition to that we need to cache this in the client or store the stats as a single blob in the database to further cut down on the time. However, the way it stands right now column stats seem unusable.





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