Coast was originally conceived as a simple, yet powerful clojure database library.
It evolved and grew from a yesql clone into a full-fledged database management library of it's own including a custom query builder, ORM (minus the O and the M), and custom clojure syntax migrations as well.
In this guide we'll learn to setup and use the database provider.
NOTE: Coast uses the java.jdbc and hikari (https://github.com/brettwooldridge/HikariCP) libraries under the hood
The list of supported databases and their drivers:
| database | driver |
|---|---|
| postgresql | pgjdbc |
| sqlite3 | sqlite-jdbc |
Coast by default installs the sqlite driver for you in the deps.edn file:
; deps.edn
{:deps {org.xerial/sqlite-jdbc {:mvn/version "3.25.2"}}}
You can install the postgres driver the same way:
; deps.edn
{:deps {org.postgresql/postgresql {:mvn/version "42.2.5"}}}
Coast has a two handy cli commands to create and drop databases in production or development:
make db/create
and
make db/drop
This uses the :coast-env key from the env.edn file (or the COAST_ENV environment variable) to determine which database from the db.edn file to create. For example given this env.edn:
{:coast-env "dev"}
and this db.edn
{:dev {:database "project_zero_dev.sqlite3"
:adapter "sqlite"}}
The file project_zero_dev.sqlite3 will be created in your project directory when you execute make db/create.
Coast uses the sqlite connection by default.
The default connection can be set via the db.edn file:
; db.edn
{:dev {:database "project_zero_dev.sqlite3"
:adapter "sqlite"}
:test {:database "project_zero_test.sqlite3"
:adapter "sqlite"}
:prod {:database #env :db-name
:adapter "sqlite"}}
Postgres can be set similarly:
; db.edn
{:dev {:database "project_zero_dev"
:adapter "postgres"}
:test {:database "project_zero_test"
:adapter "postgres"}
:prod {:database #env :db-name
:adapter "postgres"
:username #env :db-username
:password #env :db-password
:host #env :db-host
:port #env :db-port}}
Coast queries has a data-driven API, meaning all queries are clojure vectors, similar to views and the routes.
NOTE: Coast uses the singular version of all words for table names which is in opposition to most other full stack frameworks.
For example to select all people from the person table:
(coast/q '[:select * :from person])
; => [{:person/email "" :person/first-name "" :person/last-name ""}]
To add a where clause to a query, add a :where keyword to the vector:
(coast/q '[:select *
:from person
:where [first-name "sean"]])
If you need more power out of your where query, feel free to pass a sql vector instead:
(coast/q '[:select *
:from person
:where ["age > ?" 18]])
To add multiple where clauses ANDed together, add multiple vectors:
(coast/q '[:select *
:from person
:where [first-name "sean"]
["age > ?" 18]])
Multiple where clauses OR'd together? prefix with the or symbol:
(coast/q '[:select *
:from person
:where or [first-name "sean"]
["age > ?" 18]])
See the queries documentation for the complete API reference.
Coast pools connections for reuse and all used connections are maintained unless the process dies.
To close all connections, call the .close method:
(.close (:datasource (coast/connection)))
Debugging database queries can be handy in both development and production.
Coast has a very simple debugging mechanism, set :debug to true in db.edn:
{:dev {:database "project_zero_dev.sqlite3"
:adapter "sqlite"
:debug true}}
This enables printing of all sql queries to stdout.