Use jsonb field type when using Postgres backend

[sekjal]

I have submitted a PR to the silverstripe/silverstripe-postgresql repo to enable support for jsonb columns in the database, with hopes that this can be utilized by this module to facilitate better querying and performance when using Postgres as a backend. The typename was set to 'json' to be somewhat more generic than PostgreSQL's jsonb type.

I believe there is also native JSON support in MySQL's higher versions, which could be accounted for as well, should the SQL Schema Manager for that engine be updated to support the 'json' type as well.

[phptek]

Interesting. Thank you.