account_referrer_index is empty

[oxarbitrage]

i was trying to make an api call for a way to get account referrers, something better than going every account client side checking the referrer field, i found there is an index for this purposes: account_referrer_index:

https://github.com/bitshares/bitshares-core/blob/master/libraries/chain/include/graphene/chain/account_object.hpp#L303

However this index it is not being populated: https://github.com/bitshares/bitshares-core/blob/master/libraries/chain/account_object.cpp#L257-L268

Unsure if this is just incomplete or empty by something else. our options will be to populate or to send account data to ES by plugin and index by anything needed.

[abitmore]

I guess it's incomplete. IMHO account_referrer_index and account_member_index "should" be moved into a plugin, since they're not required by consensus.

//Update: according to this comment, it's not that easy to move them to a plugin.

[pmconrad]

The issue with undo_db is easily fixed, IMO. If any callbacks have been registered before the start of replay, enable undo_db, otherwise don't. Maybe log a warning about the performance hit when enabling.

[pmconrad]

Secondary indexes can easily be added in a plugin. No need to change undo_db behaviour during replay.

[abitmore]

#1918 removed account_referrer_index and moved account_member_index to a plugin.