[b0ti]

Note that this is not PG, Raijin is a new implementation and is not built on Postgres. Otherwise the question is valid. Raijin does not store NULL values though. In the above example a specific field (column) was selected and that's why it appears as null. Perhaps the output would be more appropriate this way then (which is a modification for us to consider):

  {"foo":"bar"}
  {"foo":"bar2","intfield":42}

Note that when you select the full record with the star it does not return null values:

  select * from tbl;
  --
  {"_id":1,"eventtime":"2016-07-20 10:37:12","foo":"bar","whatever":"xx"}
  {"_id":2,"eventtime":"2016-07-20 10:38:22","foo":"bar2","intfield":42}

The undef/exists thing can get a bit confusing when you are mapping this into SQL.