adding default limits when there is an offset for sqlite and mysql [#5316 state:resolved]

Manifest.txt

@@ -73,6 +73,7 @@ lib/arel/visitors/mysql.rb
 lib/arel/visitors/oracle.rb
 lib/arel/visitors/order_clauses.rb
 lib/arel/visitors/postgresql.rb
+lib/arel/visitors/sqlite.rb
 lib/arel/visitors/to_sql.rb
 lib/arel/visitors/visitor.rb
 lib/arel/visitors/where_sql.rb
@@ -98,6 +99,8 @@ test/test_select_manager.rb
 test/test_table.rb
 test/test_update_manager.rb
 test/visitors/test_join_sql.rb
+test/visitors/test_mysql.rb
 test/visitors/test_oracle.rb
 test/visitors/test_postgres.rb
+test/visitors/test_sqlite.rb
 test/visitors/test_to_sql.rb

lib/arel/table.rb

@@ -80,6 +80,10 @@ module Arel
       from(self).take amount
     end
 
+    def skip amount
+      from(self).skip amount
+    end
+
     def having expr
       from(self).having expr
     end

lib/arel/visitors.rb

@@ -1,5 +1,6 @@
 require 'arel/visitors/visitor'
 require 'arel/visitors/to_sql'
+require 'arel/visitors/sqlite'
 require 'arel/visitors/postgresql'
 require 'arel/visitors/mysql'
 require 'arel/visitors/oracle'
@@ -15,6 +16,8 @@ module Arel
       'mysql'           => Arel::Visitors::MySQL,
       'mysql2'          => Arel::Visitors::MySQL,
       'oracle_enhanced' => Arel::Visitors::Oracle,
+      'sqlite'          => Arel::Visitors::SQLite,
+      'sqlite3'         => Arel::Visitors::SQLite,
     }
 
     ENGINE_VISITORS = Hash.new do |hash, engine|

lib/arel/visitors/mysql.rb

@@ -2,6 +2,13 @@ module Arel
   module Visitors
     class MySQL < Arel::Visitors::ToSql
       private
+      ###
+      # :'(
+      # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+      def visit_Arel_Nodes_SelectStatement o
+        o.limit = 18446744073709551615 if o.offset && !o.limit
+        super
+      end
 
       def visit_Arel_Nodes_UpdateStatement o
         [

lib/arel/visitors/sqlite.rb

@@ -0,0 +1,11 @@
+module Arel
+  module Visitors
+    class SQLite < Arel::Visitors::ToSql
+      private
+      def visit_Arel_Nodes_SelectStatement o
+        o.limit = -1 if o.offset && !o.limit
+        super
+      end
+    end
+  end
+end

test/support/fake_record.rb

@@ -66,7 +66,7 @@ module FakeRecord
     attr_reader :spec, :connection
 
     def initialize
-      @spec = Spec.new(:adapter => 'sqlite3')
+      @spec = Spec.new(:adapter => 'america')
       @connection = Connection.new
     end
 

test/test_table.rb

@@ -6,6 +6,13 @@ module Arel
       @relation = Table.new(:users)
     end
 
+    describe 'skip' do
+      it 'should add an offset' do
+        sm = @relation.skip 2
+        sm.to_sql.must_be_like "SELECT FROM \"users\" OFFSET 2"
+      end
+    end
+
     describe 'primary_key' do
       it 'should return an attribute' do
         @relation.primary_key.name.must_equal :id

test/visitors/test_mysql.rb

@@ -0,0 +1,21 @@
+require 'helper'
+
+module Arel
+  module Visitors
+    describe 'the mysql visitor' do
+      before do
+        @visitor = MySQL.new Table.engine
+      end
+
+      ###
+      # :'(
+      # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+      it 'defaults limit to 18446744073709551615' do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        sql = @visitor.accept(stmt)
+        sql.must_be_like "SELECT LIMIT 18446744073709551615 OFFSET 1"
+      end
+    end
+  end
+end

test/visitors/test_sqlite.rb

@@ -0,0 +1,18 @@
+require 'helper'
+
+module Arel
+  module Visitors
+    describe 'the sqlite visitor' do
+      before do
+        @visitor = SQLite.new Table.engine
+      end
+
+      it 'defaults limit to -1' do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        sql = @visitor.accept(stmt)
+        sql.must_be_like "SELECT LIMIT -1 OFFSET 1"
+      end
+    end
+  end
+end