[jira] [Created] (HIVE-13951) GenericUDFArray should constant fold at compile time

["Sergey Zadoroshnyak (JIRA)" <ji...@apache.org>]

Sergey Zadoroshnyak created HIVE-13951:
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             Summary: GenericUDFArray should constant fold at compile time
                 Key: HIVE-13951
                 URL: https://issues.apache.org/jira/browse/HIVE-13951
             Project: Hive
          Issue Type: Bug
          Components: UDF
    Affects Versions: 1.3.0, 2.1.0
            Reporter: Sergey Zadoroshnyak


1. Hive constant propagation optimizer is enabled.  hive.optimize.constant.propagation=true;
2. Hive query: 
select array('Total','Total') from some_table;

ERROR: org.apache.hadoop.hive.ql.optimizer.ConstantPropagateProcFactory (ConstantPropagateProcFactory.java:evaluateFunction(939)) - Unable to evaluate org.apache.hadoop.hive.ql.udf.generic.GenericUDFArray@3d26c423. Return value unrecoginizable.

Details:
During compilation of query, hive checks if any subexpression of a specified expression can be evaluated to be constant and replaces such subexpression with the constant.
If the expression is a deterministic UDF and all the subexpressions are constants, the value will be calculated immediately during compilation time (not runtime)

So array is a deterministic UDF,  'Total' is string constant. So Hive tries to replace result of evaluation UDF with the constant.

But looks like, that Hive only supports primitives and struct objects.

So, array is not supported yet.






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