I think Thomas Groh hit this issue and might know a workaround.

In general, TableRowJsonCoder has been a huge pain, partially because Json
itself cannot always represent all types (numeric types are a constant
source of trouble in Json). In addition, I've found that encoding all data
into Json (which is space inefficient) is quite expensive when shuffling
that data (and bigQueryIO does do a GroupByKey on TableRows). I'm working
on a PR that will extract schema information and allow BigQueryIO to use
SchemaCoder instead of TableRowJsonCoder, however this is not quite ready
to be merged yet.

Reuven

On Wed, Jun 13, 2018 at 1:54 AM Etienne Chauchot <[EMAIL PROTECTED]>
wrote: