ScalaSql

ScalaSql is a Scala library that allows type-safe low-boilerplate querying of SQL databases, using "standard" Scala collections operations running against typed Table descriptions.

import scalasql._, SqliteDialect._

// Define your table model classes
case class City[T[_]](
    id: T[Int],
    name: T[String],
    countryCode: T[String],
    district: T[String],
    population: T[Long]
)
object City extends Table[City]

// Connect to your database (example uses in-memory sqlite, org.xerial:sqlite-jdbc:3.43.0.0)
val dataSource = new org.sqlite.SQLiteDataSource()
dataSource.setUrl(s"jdbc:sqlite:file.db")
lazy val dbClient = new scalasql.DbClient.DataSource(
  dataSource,
  config = new scalasql.Config {
    override def nameMapper(v: String) = v.toLowerCase() // Override default snake_case mapper
    override def logSql(sql: String, file: String, line: Int) = println(s"$file:$line $sql")
  }
)

dbClient.transaction{ db =>

  // Initialize database table schema and data
  db.updateRaw(os.read(os.Path("scalasql/test/resources/world-schema.sql", os.pwd)))
  db.updateRaw(os.read(os.Path("scalasql/test/resources/world-data.sql", os.pwd)))

  // Adding up population of all cities in China
  val citiesPop = db.run(City.select.filter(_.countryCode === "CHN").map(_.population).sum)
  // SELECT SUM(city0.population) AS res FROM city city0 WHERE city0.countrycode = ?
  println(citiesPop)
  // 175953614

  // Finding the 5-8th largest cities by population
  val fewLargestCities = db.run(
    City.select
        .sortBy(_.population).desc
        .drop(5).take(3)
        .map(c => (c.name, c.population))
  )
  // SELECT city0.name AS res__0, city0.population AS res__1
  // FROM city city0 ORDER BY res__1 DESC LIMIT ? OFFSET ?
  println(fewLargestCities)
  // Seq((Karachi, 9269265), (Istanbul, 8787958), (Ciudad de México, 8591309))
}

ScalaSql supports PostgreSQL, MySQL, Sqlite, and H2 databases. Support for additional databases can be easily added.

ScalaSql is a relatively new library, so please try it out, but be aware you may hit bugs or missing features! Please open Discussions for any questions, file Issues for any bugs you hit, or send Pull Requests if you are able to investigate and fix them!

Getting Started

To get started with ScalaSql, add it to your build.sc file as follows:

ivy"com.lihaoyi::scalasql:0.1.0"

Documentation

• ScalaSql Quickstart Examples: self-contained files showing how to set up ScalaSql with a variety of supported databases and perform simple DDL and SELECT/INSERT/UPDATE/DELETE operations:

  • Postgres
  • MySql
  • Sqlite
  • H2
  • HikariCP (and other connection pools)

• ScalaSql Tutorial: a structured walkthrough of how to use ScalaSql, connecting to a database and writing queries to SELECT/INSERT/UPDATE/DELETE against it to perform useful work. Ideal for newcomers to work through from top to bottom when getting started with the library.

• ScalaSql Cheat Sheet: a compact summary of the main features of ScalaSql and the syntax to make use of them.

• ScalaSql Reference: a detailed listing of ScalaSql functionality, comprehensively covering everything that ScalaSql supports, in a single easily searchable place. Ideal for looking up exactly methods/operators ScalaSql supports, looking up how ScalaSql code translates to SQL, or looking up SQL syntax to find out how to express it using ScalaSql. Useful subsections include:

  • DbApi, covering the main methods you can all to execute queries
  • Transaction, covering usage of transactions and savepoints
  • Select, Insert, Update, Delete: covering operations on the primary queries you are likely to use
  • Join, covering different kinds of joins
  • Returning, On Conflict: covering these modifiers on INSERT and UPDATE for the databases that support them
  • Expression Operations, covering the different types of Expr[T] values and the different operations you can do on each one
  • Option Operations, operations on Expr[Option[T]
  • Window Functions, With-Clauses/Common-Table-Expressions
  • Postgres, MySql, Sqlite, H2 Dialects: operations that are specific to each database that may not be generally applicable

• ScalaSql Design: discusses the design of the ScalaSql library, why it is built the way it is, what tradeoffs it makes, and how it compares to other common Scala database query libraries. Ideal for contributors who want to understand the structure of the ScalaSql codebase, or for advanced users who may need to understand enough to extend ScalaSql with custom functionality.

• Developer Docs: things you should read if you want to make changes to the com-lihaoyi/scalasql codebase

Changelog

0.1.0

• First release!

TODO

• Scala 3 support
• JSON columns
• Add datetime functions
• Make implicit ctx => for defining sql"..." snippets optional