[jira] [Created] (FLINK-14663) Distinguish unknown column stats and zero

["Kurt Young (Jira)" <ji...@apache.org>]

Kurt Young created FLINK-14663:
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             Summary: Distinguish unknown column stats and zero
                 Key: FLINK-14663
                 URL: https://issues.apache.org/jira/browse/FLINK-14663
             Project: Flink
          Issue Type: Improvement
          Components: Connectors / Hive, Table SQL / API
            Reporter: Kurt Young


When converting from hive stats to flink's column stats, we didn't check whether some columns stats is really set or just an initial value. For example:
{code:java}
// code placeholder
LongColumnStatsData longColStats = stats.getLongStats();
return new CatalogColumnStatisticsDataLong(
      longColStats.getLowValue(),
      longColStats.getHighValue(),
      longColStats.getNumDVs(),
      longColStats.getNumNulls());
{code}
 Hive `LongColumnStatsData` actually has information whether some stats is set through APIs like `isSetNumDVs()`. And the initial values are all 0, it will confuse us is it really 0 or just an initial value. 

 

We can use -1 to represent UNKNOWN value for column stats. 



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