Vertica - What happens with the projections when running the Database Designer?

Question

What happens with the old(existing) projections when running the Database Designer?

For example:

I have a query file and need to make query-bases projections? If I run the DB designer would the old projecitons will be deleted, overwritten?

Answer 1

You can specify what happens in the Database Designer wizard (not sure what they call it).

If you choose the "deploy" option it creates the new projections, refreshes them with data, and then deletes old projections it doesn't want the old ones. If you don't select that, it gives you some scripts you can run on your own that do the same thing.

I usually make Database Designer produce scripts. I look it over and then create my own scripts, based on those, that create and populate new projections. Once successful, I delete old projections on my own.

I may be overly cautious.

Answer 2

If you run in comprehensive mode, DBD will delete projections it determined are not necessary. If you run in query specific mode, it is much less likely to delete projections as the goal is to make specific queries faster and it does not know if the old projections are unnecessary.