konstantinb commented on code in PR #6359:
URL: https://github.com/apache/hive/pull/6359#discussion_r3012726545
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ql/src/test/results/clientpositive/llap/vectorized_stats.q.out:
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@@ -1207,13 +1207,13 @@ STAGE PLANS:
minReductionHashAggr: 0.99
mode: hash
outputColumnNames: _col0
- Statistics: Num rows: 1 Data size: 40 Basic stats:
COMPLETE Column stats: COMPLETE
+ Statistics: Num rows: 6144 Data size: 183480 Basic
stats: COMPLETE Column stats: COMPLETE
Review Comment:
@zabetak, this is a good example of the possible impact of the NDV==0 on
statistics' estimates. Due to the issue
https://issues.apache.org/jira/browse/HIVE-29534, the Metastore NDV (35) of the
column table_onetimestamp.val1 is getting ignored, making the NDV of the
underlying ColStatistics object 0. Later, extractNDVGroupingColumns() sets this
0 value to 1. The new estimate of 6144 is way worse than the metastore value of
35, but could be way better than the original "1" in certain queries.
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