It's quite plausible that this has nothing to do with union types I just
assumed that simple Avro schema must fully supported but that should not be
taken for granted.

On Mon, Mar 28, 2016 at 3:40 PM, Stefán Baxter <ste...@activitystream.com>
wrote:

> 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 know it's not popular to voice concerns here about Drill related matters
> but at this point I would like to advise everyone to stay clear of using
> Avro with Drill except for the most basic of cases.
>
> Regards,
>  -Stefán
>

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