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Posted to issues-all@impala.apache.org by "bharath v (JIRA)" <ji...@apache.org> on 2018/08/10 19:31:00 UTC

[jira] [Created] (IMPALA-7424) Improve in-memory representation of incremental stats

bharath v created IMPALA-7424:
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             Summary: Improve in-memory representation of incremental stats
                 Key: IMPALA-7424
                 URL: https://issues.apache.org/jira/browse/IMPALA-7424
             Project: IMPALA
          Issue Type: Improvement
          Components: Catalog
    Affects Versions: Impala 2.13.0, Impala 3.1.0
            Reporter: bharath v


Incremental stats are stored in the HMS' parameters map as plain Java Strings. This is suboptimal since Java String class internally uses UTF-16 encoding for the underlying bytes. The idea here is to switch to a byte array representation so that we can reduce the memory usage by half (8 bytes).  We can also compress the byte array using gzip compression and lazily decompress them when needed (typically during the incremental stats computation's finalization phase).

A prototype of this patch on a real-world Catalog dump showed ~54% JVM heap usage reduction (end-to-end) and ~79% reduction in the heap footprint for the incremental stats.



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