Refresh Materialized View

[Jayadevan M <maymala.jayadevan@xxxxxxxxx>]

Hello all,

A few questions about materialized views.
When I refresh a materialized view, is it a DELETE/INSERT behind the scenes?
Do we need to vacuum to reclaim space?
If a query is executed against the view when the refresh is happening, will the query see the data before the refresh started?

Does the refresh result in exclusive locking?
Regards,

Jayadevan