No dynamic dimensions spec in druid 0.7?

In my druid 0.6.x realtime spec file, i didnt specify any dimension columns.
Only the metric columns were specified and druid assumed the remaining columns were dimension columns.

However, looking at the ingestion spec doc for 0.7, I see that dimensionsSpec.dimensions is a required property.

http://druid.io/docs/0.8.0/ingestion/index.html

Does that mean I now have to specify dimension columns explicitly and druid can no longer deduce them?

No, you can still leave the field empty. The behavior did not change.