It seems we are currently unable to directly read/write json typed data. Specifically when I have a column in a table in Knime of type JSON, and I want to write this table to a Postgres DB Table (for example), I am unable to do so. Additionally, it would be nice when a source DB table has column of type JSON to also directly get JSON out without any input mapping. The only workaround I’ve come across is applying input mapping JSON → String.
I would expect this to work for the following nodes:
DB Reader
DB Writer, Updated, etc.
not exactly sure about postgres but ran into the same issue with MS SQL recently:
there are different stages when you can configure inbound reads and outbound writes. first place is the connection node, but also in subsequent nodes.
in my case, JSON wasn’t even configured in the default. But, it was also limited to JSON → String.
Might be different for Posgres, and you might be able to force it not by Knime type but by name instead - or your table accepts bulk loading (DB Loader) which “disables” type checking and expects the user to make sure datatypes are correct.
It seems to be the same for PostgreSQL. I was unable to make any kinds of write op to a table with a json type column, I did not stumble into any type inference unfortunately.