This adds a new flag -exact that will return exact counts instead of
estimates. The default is to return estimates since exact counting
on a problem shard could consume a lot of memory.
There are several places in the code where comma-ok map retrieval was
being used poorly. Some were benign, like checking existence before
issuing an unconditional delete with no cleanup. Others were potentially
far more serious: assuming that if 'ok' was true, then the resulting
pointer retrieved from the map would be non-nil. `nil` is a perfectly
valid value to store in a map of pointers, and the comma-ok syntax is
meant for when membership is distinct from having a non-zero value.
There was only one or two cases that I saw that being used correctly for
maps of pointers.
Curt Bushko
Jason Wilder
Joe LeGasse
Sebastian Borza
Mark Rushakoff
Mark Rushakoff
Cory LaNou