[jira] [Created] (DRILL-4548) Drill can not select from multiple Avro files

["Stefán Baxter (JIRA)" <ji...@apache.org>]

Stefán Baxter created DRILL-4548:
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             Summary: Drill can not select from multiple Avro files
                 Key: DRILL-4548
                 URL: https://issues.apache.org/jira/browse/DRILL-4548
             Project: Apache Drill
          Issue Type: Bug
          Components: Storage - Avro
    Affects Versions: 1.6.0, 1.7.0
            Reporter: Stefán Baxter


Hi,

I have reworked/refactored our Avro based logging system trying to make the whole Drill + Avro->Parquet experience a bit more agreeable.

Long story short I'm getting this error when selecting form multiple Avro files even though these files share the EXCACT same schema:

Error: UNSUPPORTED_OPERATION ERROR: Hash aggregate does not support schema changes
Fragment 0:0
[Error Id: 00d49aa2-5564-497e-a330-e852d5889beb on swift:31010] (state=,code=0)

We are using union types but only to allow for null values as seems to be supported by drill as per this comment in the Drill code: 
// currently supporting only nullable union (optional fields) like ["null", "some-type"].

This happens for a very simple group_by + count(*) query that only uses two fields in Avro and neither one of them uses a Union construct so and both of them contain string values in every case.

I now think this has nothing to do with the union types since the query uses only simple string, unless there is a full schema validation done on the content of the files rather then the identical Avro schema embedded in both files.



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