Refactor handling OFFER req and update should_store db method

[ogenev]

What was wrong?

We were accepting any content offered without checking if we are interested in the content.

Subtask of #313.

How was it fixed?

1. Update the should_store DB method to use get_pinned to avoid unnecessary memory copy and bump rocksdb crate version.
2. Remove the dummy should_store method when handling OFFER requests and accept only content we are interested in.

To-Do

• Add entry to the release notes (may forgo for trivial changes)
• Clean up commit history

[mrferris]

Interesting, if I'm understanding correctly this will result in a node sometimes not accepting data that it should accept.

Have you done any analysis on why & how often these false positives from key_may_exist will occur? I've glanced at the code but haven't come to a conclusion. I wonder whether it's worth the performance increase (I don't doubt that it is).

Also for what it's worth (if anything), Facebook doesn't use this function in production, at least in 2018:
facebook/rocksdb#4149

[ogenev]

Also for what it's worth (if anything), Facebook doesn't use this function in production, at least in 2018: facebook/rocksdb#4149

Hmm, It seems it is not as reliable as I expected, I will revert back to the get() method. Thanks for pointing this out!

[ogenev]

Actually, get_pinned seems more appropriate to avoid unnecessary memory copy.

[mrferris]

Great find on get_pinned, definitely looks like what we want to be using.

[mrferris]

LGTM!

[carver]

LGTM!