Hi Maurin,   both tables have to be scanned to observe SQL semantics. Otherwise, we would be changing the number of results coming out of your view. If you want the drop the second union operand, you could add a "WHERE a IS NOT NULL", and then the seocnd table will not be scanned.   Alex ... View more

Thanks for reporting this issue! Sorry for the trouble.   I was able to reproduce the issue and can confirm this is a regression from previous Impala versions.   I filed https://issues.cloudera.org/browse/IMPALA-4170 to track progress on the issue.   ... View more

Thanks for following up!   I'm pretty sure your table shoud work on more recent versions of Impala since we've fixed several Avro issues related to how schemas are defined.   As a workaround, you could try the following things: 1. In your .avsc file make all fields nullable by specifying the types a a union of null and the type like this: type:["null", "int"] 2. Also specify corresponding matching column definitions in your CREATE TABLE, i.e.   CREATE TABLE MI_FULL (col1 INT, col2 STRING, ) ROW FORMAT SERDE (the rest is exactly the same as before)   Let me know if you have questions and whether those workarounds helped! ... View more