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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