[jira] [Created] (DRILL-3462) There appears to be no way to have complex intermediate state

["Ted Dunning (JIRA)" <ji...@apache.org>]

Ted Dunning created DRILL-3462:
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             Summary: There appears to be no way to have complex intermediate state
                 Key: DRILL-3462
                 URL: https://issues.apache.org/jira/browse/DRILL-3462
             Project: Apache Drill
          Issue Type: Bug
            Reporter: Ted Dunning


After spending several frustrating days on the problem (see also DRILL-3461), it appears that there is no viable idiom for building an aggregator that has internal state that is anything more than a scalar.

What is needed is:

1) The ability to allocate a Repeated* type for use in a Workspace variables.  Currently, new works to get the basic structure, but there is no good way to allocate the corresponding vector.

2) The ability to use and to allocate a ComplexWriter in the Workspace variables.

3) The ability to write a UDAF that supports multi-phase aggregation.  It would be just fine if I simply have to write a combine method on my UDAF class.  I don't think that there is any way to infer such a combiner from the parameters and workspace variables.  An alternative API would be to have a form of the output function that is given an Iterable<OutputClass>, but that is probably much less efficient than simply having a combine method that is called repeatedly.




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