@casey Hi, can you check if this one satisfies your requirement enough?

#3069 (comment)

This PR has a good form, you have a good description and also added a test. Unfortunately we need another table to make this an efficient call. You can try your hand at this, or, if you want, I could show how to add another table into the database in the next Ordinals Coding Club. Let me know what you prefer :)

I can try adding it to table, thanks for your feedback

@raphjaph I have added a new table: RUNE_ID_TO_OUTPOINTS_BALANCE which tracks rune id to bytes array of (outpoints, balance)

Logic

1. Add table RUNE_ID_TO_OUTPOINTS_BALANCE update in index/rune_updater.rs
2. Add encode, decode scheme for bytes array of (outpoints, balance)
3. Update get_rune_specific_balances(): get exactly a map of (outpoints, balance) from rune id

Test

1. test_encode_decode_rune_to_outpoints_balance()
2. past test get_rune_specific_balances() works as intended

Runes can be in multiple outpoints so this the table should be a multi map. Also we already have the table OUTPOINT_TO_RUNE_BALANCES so we don't have to store the balance inside the new table.

The query needs a mapping from a rune id to a byte array of multiple n outpoints.

OUTPOINT_TO_RUNE_BALANCES maps an outpoint to a byte array of multiple m (rune, balances) so I would still have to go through the whole byte array to extract the balance of that specific rune, thus O(n*m)

So, I think why not also include balance of such specific rune in each out point (out point, balance of specific rune) as well, one less iteration. Thus, RUNE_ID_TO_OUTPOINTS_BALANCE, the cost of querying is greatly reduced to O(n)

@raphjaph can you check this one again,cargo test are passing on my local mac