Connecting

spec and pool read PGHOST, PGPORT, PGUSER, PGDATABASE and PGPASSWORD from the environment and fall back to ~/.pgpass for the password. Function arguments override anything from the environment.

(require '[psql.core :as pg]
         '[next.jdbc :as jdbc])

;; A plain db-spec, suitable for any next.jdbc call.
(def db (pg/spec))
(jdbc/execute! db ["SELECT 1 AS one"])

;; A HikariCP-pooled datasource.
(def pooled (pg/pool :host "db1.example.com"
                     :user "myaccount"
                     :dbname "anotherdb"
                     :password "foobar"
                     :hikari {:read-only true}))
(jdbc/execute! pooled ["SELECT 'hello from db'"])
(pg/close! pooled)

Delay creation so connection parameters are not resolved (and the pool is not opened) at load time:

(def db (delay (pg/pool)))
(jdbc/execute! @db ["SELECT 1"])

spec resolves its map as follows:

1. :dbtype defaults to "postgresql"; the current OS username seeds :user and :dbname (as psql does).
2. PGHOST / PGPORT / PGUSER / PGDATABASE override :host / :port / :user / :dbname.
3. Explicit spec arguments override everything above.
4. The password is taken from an explicit :password, then PGPASSWORD, then a ~/.pgpass match.