crystal-db

Common db api for crystal. You will need to have a specific driver to access a database.

• SQLite
• MySQL
• PostgreSQL
• ODBC
• Cassandra
• DuckDB
• Microsoft SQL Server

Installation

If you are creating a shard that will work with any driver, then add crystal-db as a dependency in shard.yml:

dependencies:
  db:
    github: crystal-lang/crystal-db

If you are creating an application that will work with some specific driver(s), then add them in shard.yml:

dependencies:
  sqlite3:
    github: crystal-lang/crystal-sqlite3

crystal-db itself will be a nested dependency if drivers are included.

Note: Multiple drivers can be included in the same application.

Documentation

• Latest API
• Crystal book

Usage

This shard only provides an abstract database API. In order to use it, a specific driver for the intended database has to be required as well:

The following example uses SQLite where ? indicates the arguments. If PostgreSQL is used $1, $2, etc. should be used. crystal-db does not interpret the statements.

require "db"
require "sqlite3"

DB.open "sqlite3:./file.db" do |db|
  # When using the pg driver, use $1, $2, etc. instead of ?
  db.exec "create table contacts (name text, age integer)"
  db.exec "insert into contacts values (?, ?)", "John Doe", 30

  args = [] of DB::Any
  args << "Sarah"
  args << 33
  db.exec "insert into contacts values (?, ?)", args: args

  puts "max age:"
  puts db.scalar "select max(age) from contacts" # => 33

  puts "contacts:"
  db.query "select name, age from contacts order by age desc" do |rs|
    puts "#{rs.column_name(0)} (#{rs.column_name(1)})"
    # => name (age)
    rs.each do
      puts "#{rs.read(String)} (#{rs.read(Int32)})"
      # => Sarah (33)
      # => John Doe (30)
    end
  end
end

Roadmap

Issues not yet addressed:

• Support non prepared statements. #25
• Time data type. (implementation details depends on actual drivers)
• Data type extensibility. Allow each driver to extend the data types allowed.
• Transactions & nested transactions. #27
• Connection pool.
• Logging
• Direct access to IO to avoid memory allocation for blobs.

Contributing

1. Fork it ( https://github.com/crystal-lang/crystal-db/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• bcardiff Brian J. Cardiff - creator, maintainer