testing/cross_backend/postgres_database.ts

Drop and recreate the public schema of a database a setup owns, so a backend that does not wipe its own database migrates and bootstraps from nothing on every run — bootstrap refuses a database that already holds an account.

The wipe takes everything, so it is tied to owned_name, the one database the setup owns, rather than to whatever URL reaches it. Create the database first (ensure_database_for_url); a missing one, a server that cannot be reached and a role that cannot connect all fail with what to check.

Options for empty_owned_database.

Create a Postgres database when it is missing, with createdb.

Which server it lands on depends on server_url. Given one, the database is created on the server that URL names: createdb connects through the URL with its database swapped for the postgres maintenance database, so host, port, role and query parameters all come from the URL, and a password goes to createdb in its environment, never its arguments. Without one, createdb reads the libpq environment (PGHOST / PGPORT / PGUSER).

Idempotent and never throws: a database that already exists is the quiet success case (is_createdb_already_exists). Any other failure — no createdb on PATH, no server, a role that may not create databases — is reported through deps.warn with createdb's own stderr, and whatever connects next reports a database that is really missing.

Create the database a Postgres URL names, on the server it names, when it is missing (ensure_database). A URL that is not postgres: — memory://, file:// — or that names no database is left alone.

Dependencies of ensure_database — the warning a failed createdb is reported with.

Whether createdb's stderr is its refusal of a database that already exists — Postgres's database "<name>" already exists, which createdb prints after database creation failed: ERROR:.

Whether url parses as a postgres: / postgresql: URL. URL.canParse alone admits a scheme-less localhost:5432/db, which it reads as protocol localhost:.

The URL protocols a Postgres connection string carries.

A database URL fit to print: the password, when there is one, replaced — in the userinfo and in the password query parameter pg and libpq also take. The whole URL rather than its host, which is empty for a socket URL that names its server in the query string.

The URL createdb connects through to create a database on the server server_url names — the same URL with its database replaced by postgres.

database_url with its database replaced by database — how a setup that spawns a second backend lands on the same server under a database nothing else uses.