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From: cloud-fan <git@git.apache.org>
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Subject: [GitHub] spark issue #14712: [SPARK-17072] [SQL] support table-level statistics gener...
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Message-Id: <20160821043406.0C8CBE00C4@git1-us-west.apache.org>
Date: Sun, 21 Aug 2016 04:34:06 +0000 (UTC)
archived-at: Sun, 21 Aug 2016 04:34:08 -0000

Github user cloud-fan commented on the issue:

    https://github.com/apache/spark/pull/14712
  
    Spark SQL already has its own metastore: `InMemoryCatalog`. And we do have an abstraction for metasotre: `ExternalCatalog`. We have 2 targets here:
    
    1. add table statistics in Spark SQL
    2. Spark SQL and Hive should recognize table statistics from each other.
    
    I think target 1 is more important, and we do need an implementation that not depend on hive features.
    
    > Actually, we desperately need spark sql to have its own metastore, because we need to persist statistics like histograms which AFAIK hive metastore doesn't support.
    
    We store table statistics in table properties, why would hive metastore not support it? Do you mean Hive can't recognize it? But I think it's ok, we should not limit our table statistics by what Hive supports.


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