WL#2441: Batched operation of rr_from_pointers and rr_from_tempfile

Affects: WorkLog-3.4   —   Status: Un-Assigned   —   Priority: Medium

rr_from_pointers and rr_from_tempfile are used
to fetch records from the handlers in SELECT queries
and UPDATE, DELETE queries after filesort have been applied.

Most handlers will be more efficient if the record read is batched.

To be able to handle this rr_from_pointers and rr_from_tempfile can
be designed similar to rr_from_cache where the loop of calling rnd_pos
is replaced with one handler call
rnd_batch_pos(array of record references, array of references,
              array of errors returned)
in handler.cc this can be easily implemented as a simple loop doing
rnd_pos for those handlers not wanting to implement rnd_batch_pos.