Csaba Ringhofer created IMPALA-14575:
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Summary: Optimize constants in HiveUdfCall
Key: IMPALA-14575
URL: https://issues.apache.org/jira/browse/IMPALA-14575
Project: IMPALA
Issue Type: Sub-task
Components: Backend, Frontend
Reporter: Csaba Ringhofer
Hive can signal to a UDF that an argument is constant with
ConstantObjectInspector:
https://github.com/apache/hive/blob/d9ec04156d84bedbaa9f8dc40c27dbb88a3b9f49/serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorUtils.java#L1440
https://github.com/apache/hive/blob/d9ec04156d84bedbaa9f8dc40c27dbb88a3b9f49/serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorUtils.java#L1512
This is used by st_ relation functions to optimize the common case of comparing
many geometries to a constant geometry:
https://github.com/apache/hive/blob/d9ec04156d84bedbaa9f8dc40c27dbb88a3b9f49/ql/src/java/org/apache/hadoop/hive/ql/udf/esri/ST_GeometryRelational.java#L93
Impala knows in c++ whether an argument is constant, but this information is
not passed to the Java side:
https://github.com/apache/impala/blob/2ac5a24dc0cfc9c9e7a1fc86cccf94cd1a2900af/common/thrift/Frontend.thrift#L41
Optimizing constants could help by:
- passing the argument from cpp to Java only once
- allowing const aware optimizations in UDFs
TODO:
only checked generic UDFs, not sure if this exists for legacy UDFs
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