Gets the column types of pages produced by this operator.
Notifies the operator that no more pages will be added and the
operator should finish processing and flush results. This method
will not be called if the Task is already failed or canceled.
Is this operator completely finished processing and no more
output pages will be produced.
Returns a future that will be completed when the operator becomes
unblocked. If the operator is not blocked, this method should return
Returns true if and only if this operator can accept an input page.
Adds an input page to the operator. This method will only be called if
Gets an output page from the operator. If no output data is currently
available, return null.
This method will always be called before releasing the Operator reference.