Foreign Key request

Gemfile

@@ -7,7 +7,7 @@ gemspec
 SOURCE         = ENV.fetch('SOURCE', :git).to_sym
 REPO_POSTFIX   = SOURCE == :path ? ''                                : '.git'
 DATAMAPPER     = SOURCE == :path ? Pathname(__FILE__).dirname.parent : 'http://github.com/datamapper'
-DM_VERSION     = '~> 1.3.0.beta'
+DM_VERSION     = '>= 1.2.0'
 DO_VERSION     = '~> 0.10.6'
 DM_DO_ADAPTERS = %w[ sqlite postgres mysql oracle sqlserver ]
 CURRENT_BRANCH = ENV.fetch('GIT_BRANCH', 'master')

README.rdoc

@@ -2,6 +2,16 @@
 
 DataMapper plugin for writing and specing migrations.
 
+- Foreign Keys support:
+- foreign_key_exists? table_name, foreign_key
+- table_exists? table
+- table_column_exists? table, column
+- enable_foreign_key_checks
+- disable_foreign_key_checks
+
+
+
+
 == Example
 
   require 'dm-migrations/migration_runner'
@@ -13,14 +23,30 @@ DataMapper plugin for writing and specing migrations.
 
   migration 1, :create_people_table do
     up do
+      # Check if table exists
+      if table_exists? :positions
+        create_table :jobs do
+          column :id,   Integer, :serial => true
+          column :name, String
+        end
+      end
       create_table :people do
         column :id,   Integer, :serial => true
         column :desc, String
+        column :job_id
+      end
+      if table_column_exists? :people, :jobs_id
+        modify_table :people do
+          add_foreign_key :job_id, :jobs
+        end
       end
     end
 
     down do
+      disable_foreign_key_checks
       drop_table :people
+      drop_table :jobs
+      enable_foreign_key_checks
     end
   end
 
@@ -30,6 +56,8 @@ DataMapper plugin for writing and specing migrations.
         # You currently have to use the underlying DB type here, rather than
         # a DataMapper type
         change_column :desc, 'text'
+
+        drop_foreign_key :job_id, :jobs
       end
     end
   end

dm-migrations.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |gem|
   gem.require_paths = [ "lib" ]
   gem.version       = DataMapper::Migrations::VERSION
 
-  gem.add_runtime_dependency('dm-core', '~> 1.3.0.beta')
+  gem.add_runtime_dependency('dm-core', '>= 1.2.0')
 
   gem.add_development_dependency('rake',  '~> 0.9.2')
   gem.add_development_dependency('rspec', '~> 1.3.2')

lib/dm-migrations/migration.rb

@@ -157,7 +157,15 @@ def select(sql, *bind_values)
         adapter.select(sql, *bind_values)
       end
     end
-
+
+    def disable_foreign_key_checks
+      execute "SET foreign_key_checks = 0"
+    end
+
+    def enable_foreign_key_checks
+      execute "SET foreign_key_checks = 1"
+    end
+
     def create_table(table_name, opts = {}, &block)
       execute TableCreator.new(adapter, table_name, opts, &block).to_sql
     end
@@ -247,6 +255,14 @@ def quoted_name
     def migration_info_table_exists?
       adapter.storage_exists?('migration_info')
     end
+
+    def table_exists? name
+      adapter.storage_exists?(name.to_s)
+    end
+
+    def table_column_exists? table, column
+      adapter.field_exists?(table.to_s, column.to_s)
+    end
 
     # Fetch the record for this migration out of the migration_info table
     def migration_record

lib/dm-migrations/sql/table_modifier.rb

@@ -19,6 +19,29 @@ def add_column(name, type, opts = {})
       @statements << "ALTER TABLE #{quoted_table_name} ADD COLUMN #{column.to_sql}"
     end
 
+    def foreign_key_exists?(constraint_name)
+      # TODO: Move to ADAPTERS
+      str = "SELECT TRUE FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE = 'FOREIGN KEY' AND TABLE_SCHEMA = '#{adapter.schema_name}' AND TABLE_NAME = '#{table_name}' AND CONSTRAINT_NAME = '#{@table_name+'_'+constraint_name.to_s.gsub('_id', '')+'_fk'}'"    
+      # puts str
+      result = @adapter.select(str)
+      # puts "Result: #{result.inspect}"
+      result.blank? ? false : (result.first == 1)
+    end
+
+    def add_foreign_key(column, reference, reference_id = 'id')
+      @statements << "ALTER TABLE #{quoted_table_name} " +
+                                  "ADD CONSTRAINT #{quote_column_name(@table_name+'_'+reference.to_s.gsub('_id', '')+'_fk')} " +
+                                  "FOREIGN KEY (#{quote_column_name(column)}) " +
+                                  "REFERENCES #{quote_column_name(reference)} (#{quote_column_name(reference_id)}) " +
+                                  "ON DELETE NO ACTION ON UPDATE NO ACTION"
+    end
+
+    def drop_foreign_key(constraint_name)
+      fk_name = quote_column_name(@table_name+'_'+constraint_name.to_s.gsub('_id', '')+'_fk')
+      @statements << "ALTER TABLE #{quoted_table_name} DROP FOREIGN KEY #{fk_name}"
+      # @statements << "ALTER TABLE #{quoted_table_name} DROP INDEX #{fk_name}"
+    end
+
     def drop_column(name)
       # raise NotImplemented for SQLite3. Can't ALTER TABLE, need to copy table.
       # We'd have to inspect it, and we can't, since we aren't executing any queries yet.

lib/dm-migrations/version.rb

@@ -1,5 +1,5 @@
 module DataMapper
   module Migrations
-    VERSION = '1.3.0.beta'
+    VERSION = '1.3.3'
   end
 end