## Problem
In f37eeb56, I properly escaped the identifier, but I haven't noticed
that the resulting string is used in the `format('...')`, so it needs
additional escaping. Yet, after looking at it closer and with Heikki's
and Tristan's help, it appeared to be that it's a full can of worms and
we have problems all over the code in places where we use PL/pgSQL
blocks.
## Summary of changes
Add a new `pg_quote_dollar()` helper to deal with it, as dollar-quoting
of strings seems to be the only robust way to escape strings in dynamic
PL/pgSQL blocks. We mimic the Postgres' `pg_get_functiondef` logic here
[1].
While on it, I added more tests and caught a couple of more bugs with
string escaping:
1. `get_existing_dbs_async()` was wrapping `owner` in additional
double-quotes if it contained special characters
2. `construct_superuser_query()` was flawed in even more ways than the
rest of the code. It wasn't realistic to fix it quickly, but after
thinking about it more, I realized that we could drop most of it
altogether. IIUC, it was added as some sort of migration, probably back
when we haven't had migrations yet. So all the complicated code was
needed to properly update existing roles and DBs. In the current Neon,
this code only runs before we create the very first DB and role. When we
create roles and DBs, all `neon_superuser` grants are added in the
different places. So the worst thing that could happen is that there is
an ancient branch somewhere, so when users poke it, they will realize
that not all Neon features work as expected. Yet, the fix is simple and
self-serve -- just create a new role via UI or API, and it will get a
proper `neon_superuser` grant.
[1]:
8b49392b27/src/backend/utils/adt/ruleutils.c (L3153)Closesneondatabase/cloud#25048
Before, compute_ctl didn't have a good registry for what command would
run when, depending exclusively on sync code to apply changes. When
users have many databases/roles to manage, this step can take a
substantial amount of time, breaking assumptions about low (re)start
times in other systems.
This commit reduces the time compute_ctl takes to restart when changes
must be applied, by making all commands more or less blind writes, and
applying these commands in an asynchronous context, only waiting for
completion once we know the commands have all been sent.
Additionally, this reduces time spent by batching per-database
operations where previously we would create a new SQL connection for
every user-database operation we planned to execute.
