Merge pull request #317 from natebird/nulls_last_performance

Improve query performance when nulls_last option is enabled

Author: n-rodriguez

lib/ajax-datatables-rails/datatable/simple_order.rb

@@ -14,11 +14,7 @@ def initialize(datatable, options = {})
       end
 
       def query(sort_column)
-        if sort_nulls_last?
-          "CASE WHEN #{sort_column} IS NULL THEN 1 ELSE 0 END, #{sort_column} #{direction}"
-        else
-          "#{sort_column} #{direction}"
-        end
+        [sort_column, direction, nulls_last_sql].compact.join(" ")
       end
 
       def column
@@ -43,6 +39,19 @@ def sort_nulls_last?
         column.nulls_last? || AjaxDatatablesRails.config.nulls_last == true
       end
 
+      def nulls_last_sql
+        return unless sort_nulls_last?
+
+        case AjaxDatatablesRails.config.db_adapter
+        when :pg, :postgresql, :postgres, :oracle
+          "NULLS LAST"
+        when :mysql, :mysql2, :sqlite, :sqlite3
+          "IS NULL"
+        else
+          raise 'unsupported database adapter'
+        end
+      end
+
     end
   end
 end

spec/ajax-datatables-rails/datatable/simple_order_spec.rb

@@ -19,7 +19,7 @@
 
       it 'sql query' do
         expect(simple_order.query('email')).to eq(
-          'CASE WHEN email IS NULL THEN 1 ELSE 0 END, email DESC'
+          "email DESC #{nulls_last_sql}"
         )
       end
     end
@@ -28,12 +28,29 @@
       let(:sorted_datatable) { DatatableOrderNullsLast.new(sample_params).datatable }
       let(:nulls_last_order) { AjaxDatatablesRails::Datatable::SimpleOrder.new(sorted_datatable, options) }
 
-      it 'sql query' do
-        expect(nulls_last_order.query('email')).to eq(
-          'CASE WHEN email IS NULL THEN 1 ELSE 0 END, email DESC'
-        )
+      context 'with postgres database adapter' do
+        before { AjaxDatatablesRails.config.db_adapter = :pg }
+
+        it 'sql query' do
+          expect(nulls_last_order.query('email')).to eq('email DESC NULLS LAST')
+        end
+      end
+
+      context 'with sqlite database adapter' do
+        before { AjaxDatatablesRails.config.db_adapter = :sqlite }
+
+        it 'sql query' do
+          expect(nulls_last_order.query('email')).to eq('email DESC IS NULL')
+        end
+      end
+
+      context 'with mysql database adapter' do
+        before { AjaxDatatablesRails.config.db_adapter = :mysql }
+
+        it 'sql query' do
+          expect(nulls_last_order.query('email')).to eq('email DESC IS NULL')
+        end
       end
     end
   end
-
 end

spec/ajax-datatables-rails/orm/active_record_sort_records_spec.rb

@@ -54,8 +54,7 @@
       datatable.params[:order]['0'] = { column: '0', dir: 'asc' }
       datatable.params[:order]['1'] = { column: '1', dir: 'desc' }
       expect(datatable.sort_records(records).to_sql).to include(
-        'ORDER BY CASE WHEN users.username IS NULL THEN 1 ELSE 0 END, users.username ASC, ' +
-        'CASE WHEN users.email IS NULL THEN 1 ELSE 0 END, users.email DESC'
+        "ORDER BY users.username ASC #{nulls_last_sql}, users.email DESC #{nulls_last_sql}"
       )
     end
   end
@@ -67,8 +66,7 @@
       nulls_last_datatable.params[:order]['0'] = { column: '0', dir: 'asc' }
       nulls_last_datatable.params[:order]['1'] = { column: '1', dir: 'desc' }
       expect(nulls_last_datatable.sort_records(records).to_sql).to include(
-        'ORDER BY users.username ASC, ' +
-        'CASE WHEN users.email IS NULL THEN 1 ELSE 0 END, users.email DESC'
+        "ORDER BY users.username ASC, users.email DESC #{nulls_last_sql}"
       )
     end
   end

spec/support/test_helpers.rb

@@ -97,3 +97,14 @@ def data
     end
   end
 end
+
+def nulls_last_sql
+  case AjaxDatatablesRails.config.db_adapter
+  when :pg, :postgresql, :postgres, :oracle
+    "NULLS LAST"
+  when :mysql, :mysql2, :sqlite, :sqlite3
+    "IS NULL"
+  else
+    raise 'unsupported database adapter'
+  end
+end