Summary:
For MDEV-19670: MyRocks: key lookups into deleted data are very slow
BaseDeltaIterator remembers iterate_upper_bound and will not let delta_iterator_
walk above the iterate_upper_bound if base_iterator_ is not valid
anymore.
== Rationale ==
The most straightforward way would be to make the delta_iterator
(which is a rocksdb::WBWIIterator) to support iterator bounds. But
checking for bounds has an extra CPU overhead.
So we put the check into BaseDeltaIterator, and only make it when
base_iterator_ is not valid.
(note: We could take it even further, and move the check a few lines
down, and only check iterator bounds ourselves if base_iterator_ is
not valid AND delta_iterator_ hit a tombstone).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5403
Differential Revision: D15863092
Pulled By: maysamyabandeh
fbshipit-source-id: 8da458e7b9af95ff49356666f69664b4a6ccf49b
230bcae7b6