A very simple database access library for Postgres, in Scala 3 Native. It is based on bindings to libpq produced by my binding generator
See blog post for details.
This is pre-alpha software - it is enough to create a functioning app, but it's tremendously incomplete and it will take a lot of time and effort to make it usable.
Examples:
- Twotm8 - basic usage, codecs and migrations
- Scala Boot - more advanced usage, including fragments
Pre-requisites:
- For runtime,
libpq5(debian) or similar has to be installed- Unless you are linking your binary statically, of course - in that case I highly recommend using sn-vcpkg: https://github.com/indoorvivants/sn-vcpkg#sbt
- For Scala Native, Clang has to be installed.
- Direct SQL usage, no ORM
- Minimal overhead on top of
libpq- unless the overhead is required to improve safety and user experience - Skunk-like codecs and
sql"..."interpolator - Direct style (no IO monad)
- Having fun
Assuming you have postgres running:
$ docker run -p 5432:5432 -e POSTGRES_PASSWORD=mysecretpassword -d postgres//> using platform "scala-native"
//> using lib "com.indoorvivants.roach::core::0.0.6"
import roach.*
import scala.util.Using
import scala.scalanative.unsafe.Zone
import roach.codecs.*
val connectionString =
"postgresql://postgres:mysecretpassword@localhost:5432/postgres"
Zone { implicit z =>
Pool.single(connectionString) { pool =>
pool.withLease {
sql"select typname, typisdefined from pg_type".all(name ~ bool).foreach(println)
// with parameters now
val oid: Option[Int] =
sql"select oid::int4 from pg_type where typname = $varchar".one("bool", int4)
}
}
}Similar to Skunk's, just a lot less advanced.
import roach.*
import roach.codecs.*
import scalanative.unsafe.*
def example(using Database, Zone) =
sql"select count(*) from my_table where x = $int4".all(25, int4)
sql"select count(*) from my_table where x = $int4 and y = $text".count(25 -> "hello")
sql"select count(*) from my_table".count()
sql"select count(*) from my_table where x = $int4 and y = $text".count(25 -> "hello")
case class Data(key: Int, value: String)
val rc = (int4 ~ text).as[Data]
val tableName = "my_table"
sql"insert into $tableName values ($rc)".exec(Data(150, "howdies"))Note that the parameters to the query are verified at compile time, not runtime, i.e. these usages will not compile:
import roach.*
import roach.codecs.*
import scalanative.unsafe.*
def example_failure(using Database, Zone) =
// Found: ("hello" : String)
// Required: Int
// sql"select count(*) from my_table where x = $int4".count("hello")
// ^^^^^^^
sql"select count(*) from my_table where x = $int4".count("hello")
// Found: (String, Int)
// Required: (Int, String)
// sql"select count(*) from my_table where x = $int4 and y = $text".count("hello" -> 25)
// ^^^^^^^^^^^^^
sql"select count(*) from my_table where x = $int4 and y = $text".count("hello" -> 25)sql interpolator produces a Query, so you can use it as described in the previous section
Fragments allow you to extract certain parts of the SQL query into a separate object and optionally apply it to some codecs, which will become inputs in the final query
import roach.*
import roach.codecs.*
import scalanative.unsafe.*
def fragments_example(using Database, Zone) =
// sharing list of fields
val normal = Fragment("key, value")
val q: Vector[(Int, String)] =
sql"select $normal from my_table where key = 25".all(int4 ~ text)
// sharing both list of fields, but also
// indicating that this fragment
// affects the input of the entire query
val withInput = normal.applied(int4 ~ text)
val q1 =
sql"insert into my_table(${withInput.sql}) values ($withInput) returning key"
val result: Option[Int] = q1.one(125 -> "yo", int4)- Circe: Available at
com.indoorvivants.roach::circe::0.0.6maven coordinates. - Upickle: Available at
com.indoorvivants.roach::upickle::0.0.6maven coordinates.
import roach.{upickle => _, circe => _, *}
import roach.codecs.*
import scalanative.unsafe.*
def circe_example(using Database, Zone) =
import roach.circe.*
// returning io.circe.Json directly
sql"""SELECT '{"bar": "baz", "balance": 7.77, "active": false}'::json""".one(json)
// returning a class with a derived codec
case class Test(hello: String, bla: Int) derives io.circe.Codec.AsObject
sql"""SELECT '{"hello": "baz", "bla": 7}'::json""".one(jsonOf[Test])
def upickle_example(using Database, Zone) =
import roach.upickle.*
// returning ujson.Value
sql"""SELECT '{"bar": "baz", "balance": 7.77, "active": false}'::json""".one(json)
// returning a class with a derived codec
case class Test(hello: String, bla: Int) derives upickle.default.ReadWriter
sql"""SELECT '{"hello": "baz", "bla": 7}'::json""".one(jsonOf[Test])For this to work, make sure you have Resource Embedding enabled.
Because in Scala Native we currently cannot have a resource listing, we need to specify all the migration files manually:
import roach.*
import roach.codecs.*
import scalanative.unsafe.*
def migrate_example(pool: Pool)(using Zone) =
Migrate.all(pool)(
ResourceFile("/v001.sql"),
ResourceFile("/v002.sql"),
ResourceFile("/v003.sql")
)The existence of those resource files will be checked at compile time, and in case the file doesn't exist, you will get a compilation error:
/v003.sql doesn't exist as a resource
ResourceFile("/v003.sql")
^^^^^^^^^^^^^^^^^^^^^^^^^
The migrations state will be persisted in a table named __roach_migrations (unless you override it using second parameter to all.
Name of the file (not the full path) is used to identify the migration.
Note that Migrate.all takes an exclusive lock of its internal table and runs all migrations within that - to prevent any concurrent modification.
