Chen Feng created HBASE-23068:
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Summary: Improve performance of InListExpression.hashCode
Key: HBASE-23068
URL: https://issues.apache.org/jira/browse/HBASE-23068
Project: HBase
Issue Type: Improvement
Reporter: Chen Feng
Assignee: Chen Feng
In WhereOptimizer.pushKeyExpressionsToScan(), has a line of code:
"extractNodes.addAll(nodesToExtract)" When executing sqls like "select * from
... where A in (a1, a2, ..., a_n) and B = X", saying A in N (N > 100,000)
elements, previous code execution will slow (> 90s in our environment).
This is because in such case, extractNodes is a HashSet, nodesToExtract is a
List with N InListExpression (the N InListExpressions are the same instance),
each InListExpression.values has N elements as well.
HashSet.addAll(list<InListExpression>) will call N times of
InListExpression.hashCode(). Each time, InListExpression.hashCode() will
calculate hashCode for every value. Therefore, the time complexity will be N^2.
A simple way to solve it is to remember of the hashCode of InListExpression and
returns it directly if calculated once.
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