Deletes all tuples in the Space. Equivalent to Clear("")

Deletes from the Space the tuples that match the specified filter on a "best effort" basis. If no filter is specified, all tuples are deleted. This operation does not block other space operations while it is ongoing, so if other clients perform write operations on entries already removed but before the clear finishes, it might be the case that the space contains tuples that match the filter after the clear completes. Thus, it is up to the application to synchronize its clients to guarantee that no write operations happen while the clear is ongoing if the intent is to clear all entries present in the space at the time clear is invoked. Internally, this operation, among other tasks, executes a series of small queries with the provided filter. Depending on the filter string and the indexing of the space, there is the possibility that one of these queries results in a linear scan that takes a significant amount of time. If that were to happen, one or more of the space seeders will log a message warning that a long query was executed some seconds after the user executes this call. To fix this problem, the user should update the filter string or add extra secondary indices in order to avoid long linear scans. Persistence behaviour When share-all persistence is used, this method does not trigger onWrite callbacks. It is user's responsibility to perform clear on the back-end database. When share-nothing persistence is used, the in memory space data is kept synchronized with the persistence files and entries are removed from file as well. Listener behaviour Listeners do not get callbacks for takes performed along with clear execution.