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 >