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Posted to dev@hive.apache.org by "Mustafa İman (Jira)" <ji...@apache.org> on 2021/01/15 00:19:00 UTC
[jira] [Created] (HIVE-24638) Redundant filter in scalar subquery
Mustafa İman created HIVE-24638:
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Summary: Redundant filter in scalar subquery
Key: HIVE-24638
URL: https://issues.apache.org/jira/browse/HIVE-24638
Project: Hive
Issue Type: Improvement
Reporter: Mustafa İman
Look at the query and CBO plan in https://issues.apache.org/jira/browse/HIVE-24595 .
Note that there is a filter to guarantee that subquery returns only one row: "HiveFilter(condition=[<=(sq_count_check($0), 1)])" . This condition is redundant as either sq_count_check fails in runtime or condition is true for all rows.
Look at the stacktrace
{code:java}
at org.apache.hadoop.hive.ql.udf.generic.GenericUDFSQCountCheck.evaluate(GenericUDFSQCountCheck.java:70) at org.apache.hadoop.hive.ql.udf.generic.GenericUDFSQCountCheck.evaluate(GenericUDFSQCountCheck.java:70) at org.apache.hadoop.hive.ql.exec.ExprNodeGenericFuncEvaluator._evaluate(ExprNodeGenericFuncEvaluator.java:197) at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:80) at org.apache.hadoop.hive.ql.exec.ExprNodeGenericFuncEvaluator$DeferredExprObject.get(ExprNodeGenericFuncEvaluator.java:88) at org.apache.hadoop.hive.ql.udf.generic.GenericUDFOPEqualOrLessThan.evaluate(GenericUDFOPEqualOrLessThan.java:111) at org.apache.hadoop.hive.ql.exec.ExprNodeGenericFuncEvaluator._evaluate(ExprNodeGenericFuncEvaluator.java:197) at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:80) at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:68) at org.apache.hadoop.hive.ql.exec.FilterOperator.process(FilterOperator.java:113) at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:888) at org.apache.hadoop.hive.ql.exec.GroupByOperator.forward(GroupByOperator.java:1004) at org.apache.hadoop.hive.ql.exec.GroupByOperator.flush(GroupByOperator.java:1028)
{code}
GenericUDFOPEqualOrLessThan is redundant here as GenericUDFSQCountCheck does the same check.
Instead of this filter we can have HiveProject(sq_count_check($0))
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