Add MSSQL support for Database#foreign_key_list

lib/sequel/adapters/shared/mssql.rb

@@ -13,6 +13,7 @@ module DatabaseMethods
       SQL_ROLLBACK_TO_SAVEPOINT = 'IF @@TRANCOUNT > 0 ROLLBACK TRANSACTION autopoint_%d'.freeze
       SQL_SAVEPOINT = 'SAVE TRANSACTION autopoint_%d'.freeze
       MSSQL_DEFAULT_RE = /\A(?:\(N?('.*')\)|\(\((-?\d+(?:\.\d+)?)\)\))\z/
+      FOREIGN_KEY_ACTION_MAP = {0 => :no_action, 1 => :cascade, 2 => :set_null, 3 => :set_default}.freeze
 
       include Sequel::Database::SplitAlterTable
 
@@ -36,6 +37,47 @@ def global_index_namespace?
         false
       end
 
+      # Return foreign key information using the system views, including
+      # :name, :on_delete, and :on_update entries in the hashes.
+      def foreign_key_list(table, opts={})
+        m = output_identifier_meth
+        im = input_identifier_meth
+        schema, table = schema_and_table(table)
+        current_schema = m.call(get(Sequel.function('schema_name')))
+        fk_action_map = FOREIGN_KEY_ACTION_MAP
+        ds = metadata_dataset.from(:sys__foreign_keys___fk).
+          join(:sys__foreign_key_columns___fkc, :constraint_object_id => :object_id).
+          join(:sys__all_columns___pc, :object_id => :fkc__parent_object_id,     :column_id => :fkc__parent_column_id).
+          join(:sys__all_columns___rc, :object_id => :fkc__referenced_object_id, :column_id => :fkc__referenced_column_id).
+          where{{object_schema_name(:fk__parent_object_id) => im.call(schema || current_schema)}}.
+          where{{object_name(:fk__parent_object_id) => im.call(table)}}.
+          select{[:fk__name, 
+                  :fk__delete_referential_action, 
+                  :fk__update_referential_action, 
+                  :pc__name___column, 
+                  :rc__name___referenced_column, 
+                  object_schema_name(:fk__referenced_object_id).as(:schema), 
+                  object_name(:fk__referenced_object_id).as(:table)]}.
+          order(:name)
+        h = {}
+        ds.each do |row|
+          if r = h[row[:name]]
+            r[:columns] << m.call(row[:column])
+            r[:key] << m.call(row[:referenced_column])
+          else
+            referenced_schema = m.call(row[:schema])
+            referenced_table = m.call(row[:table])
+            h[row[:name]] = { :name      => m.call(row[:name]), 
+                              :table     => (referenced_schema == current_schema) ? referenced_table : :"#{referenced_schema}__#{referenced_table}",
+                              :columns   => [m.call(row[:column])], 
+                              :key       => [m.call(row[:referenced_column])], 
+                              :on_update => fk_action_map[row[:update_referential_action]], 
+                              :on_delete => fk_action_map[row[:delete_referential_action]] }
+          end
+        end
+        h.values
+      end
+
       # Use the system tables to get index information
       def indexes(table, opts={})
         m = output_identifier_meth

spec/adapters/mssql_spec.rb

@@ -568,3 +568,81 @@ def transaction(opts={})
     MSSQL_DB[:test__items].columns.should == [:id]
   end
 end
+
+describe "Database#foreign_key_list" do
+  before(:all) do
+    MSSQL_DB.create_table! :items do
+      primary_key :id
+      integer     :sku
+    end
+    MSSQL_DB.create_table! :prices do
+      integer     :item_id
+      datetime    :valid_from
+      float       :price
+      primary_key [:item_id, :valid_from]
+      foreign_key [:item_id], :items, :key => :id, :name => :fk_prices_items
+    end
+    MSSQL_DB.create_table! :sales do
+      integer  :id
+      integer  :price_item_id
+      datetime :price_valid_from
+      foreign_key [:price_item_id, :price_valid_from], :prices, :key => [:item_id, :valid_from], :name => :fk_sales_prices, :on_delete => :cascade
+    end
+  end
+  after(:all) do
+    MSSQL_DB.drop_table :sales
+    MSSQL_DB.drop_table :prices
+    MSSQL_DB.drop_table :items
+  end
+  it "should support typical foreign keys" do
+    MSSQL_DB.foreign_key_list(:prices).should == [{:name      => :fk_prices_items, 
+                                                   :table     => :items, 
+                                                   :columns   => [:item_id], 
+                                                   :key       => [:id], 
+                                                   :on_update => :no_action, 
+                                                   :on_delete => :no_action }]
+  end
+  it "should support a foreign key with multiple columns" do
+    MSSQL_DB.foreign_key_list(:sales).should == [{:name      => :fk_sales_prices, 
+                                                  :table     => :prices, 
+                                                  :columns   => [:price_item_id, :price_valid_from], 
+                                                  :key       => [:item_id, :valid_from], 
+                                                  :on_update => :no_action, 
+                                                  :on_delete => :cascade }]
+  end
+
+  context "with multiple schemas" do
+    before(:all) do
+      MSSQL_DB.execute_ddl "create schema vendor"
+      MSSQL_DB.create_table! :vendor__vendors do
+        primary_key :id
+        varchar     :name
+      end
+      MSSQL_DB.create_table! :vendor__mapping do
+        integer :vendor_id
+        integer :item_id
+        foreign_key [:vendor_id], :vendor__vendors, :name => :fk_mapping_vendor
+        foreign_key [:item_id], :items, :name => :fk_mapping_item
+      end
+    end
+    after(:all) do
+      MSSQL_DB.drop_table :vendor__mapping
+      MSSQL_DB.drop_table :vendor__vendors
+      MSSQL_DB.execute_ddl "drop schema vendor"
+    end
+    it "should support mixed schema bound tables" do
+      MSSQL_DB.foreign_key_list(:vendor__mapping).should == [{:name      => :fk_mapping_item, 
+                                                              :table     => :items, 
+                                                              :columns   => [:item_id], 
+                                                              :key       => [:id], 
+                                                              :on_update => :no_action, 
+                                                              :on_delete => :no_action },
+                                                             {:name      => :fk_mapping_vendor, 
+                                                              :table     => :vendor__vendors, 
+                                                              :columns   => [:vendor_id], 
+                                                              :key       => [:id], 
+                                                              :on_update => :no_action, 
+                                                              :on_delete => :no_action }]
+    end
+  end
+end