Search account domain in lowercase

[abcang]

I noticed that the validation query before saving the remote account did not work with the index.

SELECT  1 AS one FROM "accounts" WHERE "accounts"."username" = 'abcang' AND "accounts"."domain" = 'pawoo.net' LIMIT 1

Limit  (cost=0.00..12043.92 rows=1 width=0) (actual time=336.947..336.948 rows=1 loops=1)
  ->  Seq Scan on accounts  (cost=0.00..12043.92 rows=1 width=0) (actual time=336.945..336.945 rows=1 loops=1)
        Filter: (((username)::text = 'abcang'::text) AND ((domain)::text = 'pawoo.net'::text))
        Rows Removed by Filter: 34062
Planning time: 0.191 ms
Execution time: 337.147 ms

Since the index of the account is as follows, it is necessary to compare it with lower("accounts"." username") and lower("accounts"."domain") to use index.

t.index "lower((username)::text), lower((domain)::text)", name: "index_accounts_on_username_and_domain_lower", unique: true

As a result of the fix, the index is now used correctly.

SELECT  1 AS one FROM "accounts" WHERE LOWER("accounts"."username") = 'abcang' AND LOWER("accounts"."domain") = 'pawoo.net' LIMIT 1

Limit  (cost=0.41..8.43 rows=1 width=0) (actual time=0.047..0.047 rows=1 loops=1)
  ->  Index Scan using index_accounts_on_username_and_domain_lower on accounts  (cost=0.41..8.43 rows=1 width=0) (actual time=0.046..0.046 rows=1 loops=1)
        Index Cond: ((lower((username)::text) = 'abcang'::text) AND (lower((domain)::text) = 'pawoo.net'::text))
Planning time: 5.180 ms
Execution time: 0.073 ms

Also, the remote account is validated with case_sensitive: true, but the actual unique index is not case-sensitive, so this was also fixed.

[abcang]

Even if the comparison target is nil, comparison with lower("accounts"."domain") is required to use the index.

[abcang]

In fact, this test was wrong. When saving the account without validating the username, an error occurred due to unique constraint of DB.

[ClearlyClaire]

Seems ok with current practices, but technically, the local part of acct URIs is supposed to be case-sensitive.

[Gargron]

technically, the local part of acct URIs is supposed to be case-sensitive.

I don't think that's true? alice is not supposed to be available when Alice exists, in fact I remember us having some issues and a migration to fix them around this.

[ClearlyClaire]

@Gargron the specs say that the local part of acct: URIs are supposed to be case-sensitive. It's just that in Mastodon we explicitly decided to go against that, to accommodate with people changing the casing of already-existing accounts manually, iirc

EDIT: but anyway, we already make that assumption in various places, so this PR shouldn't break anything that wasn't already broken