gEFBe88Z

1class Blog < Sequel::Model(:blogs)
2  set_schema do
3    primary_key :id
4    varchar :name
5    varchar :subdomain
6  end
7  
8  module Sequel
9  class Model
10    # Create a class for renaming and modifying the model's table info
11    class Migration
12      include Sequel::Schema::SQL
13      attr_reader :db, :table_name
14      def initialize(db, table_name)
15        @db, @table_name = db, table_name
16      end
17
18      def get_column_type(column_name)
19        if (column = db.table_columns(table_name)[column_name.to_s])
20          column[:Type]
21        end
22      end
23      
24      def rename_column(names = {})
25        names.each_pair do |old_name, new_name|
26          modify_column(old_name, :name => new_name)
27        end
28      end
29      
30      def modify_column(column_name, opts = {})
31        opts[:name] ||= column_name
32        opts[:type] ||= get_column_type(column_name)
33        raise "Can't get column type for #{column_name}" unless opts[:type]
34        db.execute("ALTER TABLE `#{table_name}` CHANGE #{column_name} #{column_definition_sql(opts)}")
35      end
36    end
37    
38    # Let the user call "migrate" on a model to bring it up to date
39    class << self
40      def migration
41        Migration.new(db, table_name)
42      end
43      
44      # Executes +sql+ if the model's table is not up to date
45      def migrate(sql = nil)
46        if (memory_revision = get_memory_revision) < (table_revision = get_table_revision)
47          set_memory_revision(memory_revision += 1)
48        else
49          db.query(sql) if sql
50          yield migration if block_given?
51          table_revision += 1
52          set_table_revision(table_revision)
53          set_memory_revision(table_revision)
54        end
55      end
56
57      alias :model_migration_drop_table :drop_table
58      def drop_table
59        model_migration_drop_table
60        # Reset the table revision counter when we drop a table
61        set_table_revision(0)
62      end
63      
64      def create_table
65        db.create_table_sql_list(*schema.create_info).each {|s| db << s}
66      end
67
68      def start_at_revision(revision = 0) set_memory_revision(revision) end
69
70    protected
71      # Gets the current migration revision stored in memory.
72      def get_memory_revision
73        @memory_revision || 0
74      end
75    
76      # Sets the current migration revision stored in memory.
77      def set_memory_revision(revision = 0)
78        @memory_revision = revision
79      end
80    
81      # Gets the current migration revision stored in the database. Returns a
82      # tuple: [major, minor] (e.g. [2, 0])
83      def get_table_revision
84        r = table_revisions_dataset.filter(:table_name => table_name.to_s).first
85        r ? r[:major] : 0
86      end
87    
88      # Sets the current migration  version stored in the database.
89      def set_table_revision(revision = 0)
90        dataset = table_revisions_dataset.filter(:table_name => table_name.to_s)
91        if dataset.first
92          dataset.update(:major => revision, :minor => 0)
93        else
94          dataset << {:table_name => table_name.to_s, :major => revision, :minor => 0}
95        end
96      end
97    
98      # Returns the dataset for the table_revisions table. If no such table
99      # exists, it is automatically created.
100      def table_revisions_dataset
101        unless db.table_exists?(:table_revisions)
102          db.create_table(:table_revisions) do
103            primary_key :id
104            text :table_name
105            integer :major, :default => 0
106            integer :minor, :default => 0
107          end
108        end
109        db[:table_revisions]
110      end
111    end
112  end
113end