Refactor HairTrigger builder to support referencing old and new tables

.github/workflows/workflow.yml

@@ -3,7 +3,7 @@ on:
   push:
     branches:
       - master
-  pull_request: {}
+  pull_request:
 jobs:
   test:
     runs-on: ubuntu-latest

lib/hair_trigger/builder.rb

@@ -82,6 +82,18 @@ def of(*columns)
       options[:of] = columns
     end
 
+    def old_as(table)
+      raise DeclarationError, "`old_as' requested, but no table_name specified" unless table.present?
+      options[:referencing] ||= {}
+      options[:referencing][:old] = table
+    end
+
+    def new_as(table)
+      raise DeclarationError, "`new_as' requested, but no table_name specified" unless table.present?
+      options[:referencing] ||= {}
+      options[:referencing][:new] = table
+    end
+
     def declare(declarations)
       options[:declarations] = declarations
     end
@@ -159,7 +171,7 @@ def set_#{method}(*args, &block)
         METHOD
       end
     end
-    chainable_methods :name, :on, :for_each, :before, :after, :where, :security, :timing, :events, :all, :nowrap, :of, :declare
+    chainable_methods :name, :on, :for_each, :before, :after, :where, :security, :timing, :events, :all, :nowrap, :of, :declare, :old_as, :new_as
 
     def create_grouped_trigger?
       adapter_name == :mysql || adapter_name == :trilogy
@@ -306,6 +318,10 @@ def chained_calls_to_ruby(join_str = '.')
             "where(#{prepared_where.inspect})"
           when :of
             "of(#{options[:of].inspect[1..-2]})"
+          when :old_as
+            "old_as(#{options[:referencing][:old].inspect})"
+          when :new_as
+            "new_as(#{options[:referencing][:new].inspect})"
           when :for_each
             "for_each(#{options[:for_each].downcase.to_sym.inspect})"
           when :declare
@@ -405,6 +421,23 @@ def supports_of?
       end
     end
 
+    def referencing_clause(check_support = true)
+      if options[:referencing] && (!check_support || supports_referencing?)
+        "REFERENCING " + options[:referencing].map{ |k, v| "#{k.to_s.upcase} TABLE AS #{v}" }.join(" ")
+      end
+    end
+
+    def supports_referencing?
+      case adapter_name
+      when :sqlite, :mysql
+        false
+      when :postgresql, :postgis
+        db_version >= 100000
+      else
+        false
+      end
+    end
+
     def generate_drop_trigger
       case adapter_name
         when :sqlite, :mysql, :trilogy
@@ -433,6 +466,7 @@ def generate_trigger_postgresql
       raise GenerationError, "security cannot be used in conjunction with nowrap" if options[:nowrap] && options[:security]
       raise GenerationError, "where can only be used in conjunction with nowrap on postgres 9.0 and greater" if options[:nowrap] && prepared_where && db_version < 90000
       raise GenerationError, "of can only be used in conjunction with nowrap on postgres 9.1 and greater" if options[:nowrap] && options[:of] && db_version < 90100
+      raise GenerationError, "referencing can only be used on postgres 10.0 and greater" if options[:referencing] && db_version < 100000
 
       sql = ''
 
@@ -472,6 +506,7 @@ def generate_trigger_postgresql
 
       [sql, <<-SQL]
 CREATE TRIGGER #{prepared_name} #{options[:timing]} #{options[:events].join(" OR ")} #{of_clause}ON #{adapter.quote_table_name(options[:table])}
+#{referencing_clause}
 FOR EACH #{options[:for_each]}#{prepared_where && db_version >= 90000 ? " WHEN (" + prepared_where + ')': ''} EXECUTE PROCEDURE #{trigger_action};
       SQL
     end

spec/builder_spec.rb

@@ -253,6 +253,12 @@ def builder(name = nil)
       expect(trigger.generate.grep(/AFTER UPDATE OF bar, baz/).size).to eql(1)
     end
 
+    it "should reject use of referencing pre-10.0" do
+      expect {
+        builder.on(:foos).after(:update).new_as("new_table").old_as("old_table"){ "FOO" }.generate
+      }.to raise_error /referencing can only be used on postgres 10.0 and greater/
+    end
+
     it "should accept security" do
       expect(builder.on(:foos).after(:update).security(:invoker){ "FOO" }.generate.
         grep(/SECURITY/).size).to eql(0) # default, so we don't include it
@@ -310,6 +316,17 @@ def builder(name = nil)
         to match(/DECLARE\s*foo INT;\s*BEGIN\s*FOO/)
     end
 
+    context ">= 10.0" do
+      before(:each) do
+        @adapter = MockAdapter.new("postgresql", :postgresql_version => 100000)
+      end
+
+      it "should accept `new_as' and `old_as' tables" do
+        trigger = builder.on(:foos).after(:update).new_as("new_table").old_as("old_table"){ "FOO" }
+        expect(trigger.generate.grep(/REFERENCING NEW TABLE AS new_table OLD TABLE AS old_table/).size).to eql(1)
+      end
+    end
+
     context "legacy" do
       it "should reject truncate pre-8.4" do
         @adapter = MockAdapter.new("postgresql", :postgresql_version => 80300)