tdunning commented on pull request #2432:
URL: https://github.com/apache/drill/pull/2432#issuecomment-1018676376


   The meaning of the compression parameter became a bit more strict in this
   latest version. As such, the digest should be a bit smaller and tails
   should be a bit more accurate. It is OK to increase the compression
   parameter if you want, but it has to be recognized that the results are
   approximate and a bit randomized.
   
   Can you describe a bit more about what the test is looking at?  I could
   comment more specifically about what to expect if you like.
   
   
   
   On Fri, Jan 21, 2022 at 3:55 AM James Turton ***@***.***>
   wrote:
   
   > Hi @tdunning <https://github.com/tdunning>. This PR includes an update of
   > t-digest from 3.2 to 3.3 and I think that has caused a unit test of
   > metastore statistics to fail with
   >
   > Error:  Failures:
   > Error:    TestAnalyze.testHistogramWithDataTypes1:501 Did not find 
expected pattern in plan: Filter\(condition.*\).*rowcount = 676.*,.*
   >
   > , where what's changed is the row count estimate for the results of an
   > integer inequality predicate store_id < 15 which has gone from 676 to
   > 699. Have some approximate stats computed by t-digest shifted in this
   > version, e.g. an accuracy improvement? If so, and this is expected, then
   > I'll update the unit test's expectations accordingly...
   >
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