Can i join tables from PostGres and BigQuery in one big query?

This is a feature that currently only available in the hosted version of Redash. We do plan to open source it, but currently no ETA.

Update 22/2/2018: the ability to run queries on query results (which allows joining data across multiple data sources) is available in the open source version since V3.


Depending on the size of the data you want to join, you could use python as a datasource to join the result of 2 separate queries across 2 different datasources.
Arikfr made an example here:

I’ve created a simple Python object that makes combining results from multiple data source really easy, it’s available here if you’re interested -

How to query when combining multiple datasources in one query in the hosted version of Redash?