Ashutosh Chauhan created HIVE-16909:
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Summary: Improve ndv estimates when ndvs are aggregated across
partitions
Key: HIVE-16909
URL: https://issues.apache.org/jira/browse/HIVE-16909
Project: Hive
Issue Type: Improvement
Components: Metastore, Statistics
Reporter: Ashutosh Chauhan
Tasks involved:
1. Switch over from FM-sketch to HLL bit vectors to compute ndvs.
2. Store these bit vectors in RDBMS metastore. This code already exists for
HBase metastore.
3. Combine bit vectors requested for partition list to get better ndv estimate.
This can be done initially only for CachedStore to avoid implementation
complexity.
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