HLm2Wu4A

1require 'pg'
2require 'uri'
3
4class Migrator
5
6  class Migration
7    def initialize(connection, path)
8      @connection, @path = connection, path
9    end
10
11    def execute
12      unless migration_run?
13        @connection.exec(sql)
14        record_migration
15      end
16    end
17
18    private
19
20    def migration_run?
21      count = 0
22
23      result = @connection.exec_params(
24        "SELECT COUNT(*) AS count FROM migrations WHERE version = $1",
25        [version]
26      )
27
28      count = result[0]["count"].to_i
29      result.clear()
30
31      count == 1
32    end
33
34    def sql
35      File.read(@path)
36    end
37
38    def record_migration
39      @connection.exec_params(
40        "INSERT INTO migrations (version) VALUES ($1)", 
41        [version.to_s]
42      )
43    end
44
45    def version
46      matches = File.basename(@path).match(/\A(\d+)/)
47      matches[1].to_i
48    end
49  end
50
51  def initialize(database_url, migrations_path)
52    @database_url    = database_url
53    @migrations_path = migrations_path
54  end
55
56  def migrate
57    create_migrations_table
58    migrations.map(&:execute)
59  end
60
61  private
62
63  def ignore
64    -> (r) { }
65  end
66
67  def connection
68    @connection ||= begin
69      conn = PG::Connection.open(connection_options)
70      conn.set_notice_receiver(&ignore)
71      conn
72    end
73  end
74
75  def uri
76    @uri ||= URI(@database_url)
77  end
78
79  def connection_options
80    {
81      host:     uri.host,
82      user:     uri.user,
83      password: uri.password,
84      port:     uri.port || 5432,
85      dbname:   uri.path[1..-1]
86
87    }
88  end
89
90  def files
91    Dir.glob(@migrations_path.expand_path.join("*.sql")).sort
92  end
93
94  def migrations
95    files.map {|f| Migration.new(connection, f) }
96  end
97
98  def create_migrations_table
99    connection.exec("
100      CREATE TABLE IF NOT EXISTS migrations (
101        version INTEGER NOT NULL UNIQUE
102      );
103    ")
104  end
105end