regression and improvements in handling NULLs in joins
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Key: HIVE-1605
URL: https://issues.apache.org/jira/browse/HIVE-1605
Project: Hadoop Hive
Issue Type: Improvement
Reporter: Ning Zhang
Assignee: Ning Zhang
There are regressions in sort-merge map join after HIVE-741. There are a lot of
OOM exceptions in SMBMapJoinOperator. This caused by the HashMap maintained for
each key to remember whether it is NULL. This takes too much memory when the
tables are large.
A second issu is in handling NULLs if the join keys are more than 1 column.
This appears in regular MapJoin as well as SMBMapJoin. The code only checks if
all the columns are NULL. It should return false in match if any joined value
is NULL.
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