6.3.1 Efficiently Recovering the WS
Consider a WS segment, Sr, of a projection with a sort
key K and a key range R on a recovering site r along with
a collection C of other projections, M1, …, Mb which
contain the sort key of Sr. The tuple mover guarantees
that each WS segment, S, contains all tuples with an
insertion timestamp later than some time tlastmove(S), which
represents the most recent insertion time of any record in
S’s corresponding RS segment.
To recover, the recovering site first inspects every
projection in C for a collection of columns that covers the
key range K with each segment having tlastmove(S) ≤
tlastmove(Sr). If it succeeds, it can run a collection of queries
of the form: