add index for chain.addres_preimages.address_data

[Andrew7234]

@lukaw3d pointed out that the /events endpoint was slow. Root cause was the left join on address_preimages in order to look up token-specific information for events.

[pro-wh]

I always approve these sort of changes that describe what's already done

🥲 here's us using a database table to compute a hash

[mitjat]

Thank you!

Just stating what we've discussed between the lines: The cleaner alternative would be to compute the hash in postgres.

My understanding is that the hash in question is keccak-256 here. It is potentially accessible in postgres via the no-root-required pgcrypto extension, which "supports all digest algorithms supported by OpenSSL". OpenSSL added support for keccak-256 back in Sept 2020, but at least my local install doesn't support it yet (openssl list -digest-algorithms and openssl version), nor does the one in our docker images. So this relatively ugly index is probably the right call :)