Cleanup unused fork_database::_unlinked_index?

[abitmore]

According to code:

bitshares-core/libraries/chain/fork_database.cpp

Lines 68 to 69 in bf263b1

	throw;
	_unlinked_index.insert( item );

_unlinked_index.insert(...) should have never been called.

I guess we can remove the member variable _unlinked_index?

[jmjatlanta]

It appears to me that if you attempt to push a block that is unlinkable, it should go in here. _push_block() will remove it from this collection if the problem is later resolved.

But meanwhile, it is used by is_known_block() and fetch_block().

So, without understanding all the mechanics, I would think that we should find out the intent of this collection, and if it is valid functionality, swap lines 68 and 69. If the intent is invalid, then I agree, remove _unlink_index.

To answer the question above, I need to know what causes an unlinkable_block_exception that is only temporary, and may later get resolved. I am researching, but if you know off the top of your head, please point me in the right direction.

[abitmore]

This is low priority. We'll discuss later.

By now, please primarily focus on things in 201806 hf milestone; if nothing is there, work on things in 201806 non-hf milestone (quite some are there but I think we have to postpone some, so please spend time selectively). Deadline is this Wednesday/Thursday.

[pmconrad]

If you receive blocks in order 1, 3, 2 then you'll get an unlinkable exception when trying to push 3 (because it is based on 2, but you haven't seen 2 yet).

[pmconrad]

Will be resolved by #1360

[pmconrad]

#1360 was in recent feature release. Closing.