y6ehRibL

1module Sequel
2  class Model
3    # Create a class for renaming and modifying the model's table info
4    class Migration
5      include Sequel::Schema::SQL
6      attr_reader :db, :table_name
7      def initialize(db, table_name)
8        @db, @table_name = db, table_name
9      end
10
11      def get_column_type(column_name)
12        if (column = db.table_columns(table_name)[column_name.to_s])
13          column[:Type]
14        end
15      end
16      
17      def rename_column(names = {})
18        names.each_pair do |old_name, new_name|
19          modify_column(old_name, :name => new_name)
20        end
21      end
22      
23      def modify_column(column_name, opts = {})
24        opts[:name] ||= column_name
25        opts[:type] ||= get_column_type(column_name)
26        raise "Can't get column type for #{column_name}" unless opts[:type]
27        db.execute("ALTER TABLE `#{table_name}` CHANGE #{column_name} #{column_definition_sql(opts)}")
28      end
29    end
30    
31    # Let the user call "migrate" on a model to bring it up to date
32    class << self
33      def migration
34        Migration.new(db, table_name)
35      end
36      
37      # Executes +sql+ if the model's table is not up to date
38      def migrate(sql = nil)
39        if (memory_revision = get_memory_revision) < (table_revision = get_table_revision)
40          set_memory_revision(memory_revision += 1)
41        else
42          db.query(sql) if sql
43          yield migration if block_given?
44          table_revision += 1
45          set_table_revision(table_revision)
46          set_memory_revision(table_revision)
47        end
48      end
49
50      alias :model_migration_drop_table :drop_table
51      def drop_table
52        model_migration_drop_table
53        # Reset the table revision counter when we drop a table
54        set_table_revision(0)
55      end
56      
57      def create_table
58        db.create_table_sql_list(*schema.create_info).each {|s| db << s}
59      end
60
61      def start_at_revision(revision = 0) set_memory_revision(revision) end
62
63    protected
64      # Gets the current migration revision stored in memory.
65      def get_memory_revision
66        @memory_revision || 0
67      end
68    
69      # Sets the current migration revision stored in memory.
70      def set_memory_revision(revision = 0)
71        @memory_revision = revision
72      end
73    
74      # Gets the current migration revision stored in the database. Returns a
75      # tuple: [major, minor] (e.g. [2, 0])
76      def get_table_revision
77        r = table_revisions_dataset.filter(:table_name => table_name.to_s).first
78        r ? r[:major] : 0
79      end
80    
81      # Sets the current migration  version stored in the database.
82      def set_table_revision(revision = 0)
83        dataset = table_revisions_dataset.filter(:table_name => table_name.to_s)
84        if dataset.first
85          dataset.update(:major => revision, :minor => 0)
86        else
87          dataset << {:table_name => table_name.to_s, :major => revision, :minor => 0}
88        end
89      end
90    
91      # Returns the dataset for the table_revisions table. If no such table
92      # exists, it is automatically created.
93      def table_revisions_dataset
94        unless db.table_exists?(:table_revisions)
95          db.create_table(:table_revisions) do
96            primary_key :id
97            text :table_name
98            integer :major, :default => 0
99            integer :minor, :default => 0
100          end
101        end
102        db[:table_revisions]
103      end
104    end
105  end
106end