Greg wrote:

> What about also making input prevouts filter based on the scriptpubkey being

> _spent_?  Layering wise in the processing it's a bit ugly, but if you

> validated the block you have the data needed.

AFAICT, this would mean that in order for a new node to catch up the filter

index (index all historical blocks), they'd either need to: build up a

utxo-set in memory during indexing, or would require a txindex in order to

look up the prev out's script. The first option increases the memory load

during indexing, and the second requires nodes to have a transaction index

(and would also add considerable I/O load). When proceeding from tip, this

doesn't add any additional load assuming that your synchronously index the

block as you validate it, otherwise the utxo set will already have been

updated (the spent scripts removed).

I have a script running to compare the filter sizes assuming the regular

filter switches to include the prev out's script rather than the prev

outpoint itself. The script hasn't yet finished (due to the increased I/O

load to look up the scripts when indexing), but I'll report back once it's

finished.