Zoltan Haindrich created HIVE-19501:
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Summary: Fix HyperLogLog to be threadsafe
Key: HIVE-19501
URL: https://issues.apache.org/jira/browse/HIVE-19501
Project: Hive
Issue Type: Bug
Reporter: Zoltan Haindrich
not sure if this is an issue in reality or not; but there are 3 static fields
in HyperLogLog which are rewritten during working; if there are multiple
threads are calculating HLL in the same JVM, there is a theoretical chance that
they might overwrite eachothers value...
static fields:
https://github.com/apache/hive/blob/8028ce8a4cf5a03e2998c33e032a511fae770b47/standalone-metastore/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HyperLogLog.java#L65
usage:
https://github.com/apache/hive/blob/8028ce8a4cf5a03e2998c33e032a511fae770b47/standalone-metastore/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HyperLogLog.java#L216
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