Why has the format of object value in my Sigma query result changed?

As of September 3rd 2020, Sigma supports queries using Prestosql v334 SQL syntax. As a part of this change, object (such as map, array, etc) values are now encoded in JSON format.

For example:

SELECT id, map_agg(key, value) AS dictionary FROM charges_metadata GROUP BY id

Old behavior:

id, dictionary
ch_123,{a=123, b=hello world}
...

New behavior:

id, dictionary
ch_123,"{""a"":""123"",""b"":""hello world""}"