Merge branch 'master' into set_binds

* master: (2794 commits)
  doc, API example on how to use `Model#exists?` with multiple IDs. [ci skip]
  Restore DATABASE_URL even if it's nil in connection_handler test
  [ci skip] - error_messages_for has been deprecated since 2.3.8 - lets reduce any confusion for users
  Ensure Active Record connection consistency
  Revert "ask the fixture set for the sql statements"
  Check `respond_to` before delegation due to: https://github.com/ruby/ruby/commit/d781caaf313b8649948c107bba277e5ad7307314
  Adding Hash#compact and Hash#compact! methods
  MySQL version 4.1 was EOL on December 31, 2009 We should at least recommend modern versions of MySQL to users.
  clear cache on body close so that cache remains during rendering
  add a more restricted codepath for templates fixes #13390
  refactor generator tests to use block form of Tempfile
  Fix typo [ci skip]
  Move finish_template as the last public method in the generator
  Minor typos fix [ci skip]
  make `change_column_null` reversible. Closes #13576.
  create/drop test and development databases only if RAILS_ENV is nil
  Revert "Speedup String#to"
  typo fix in test name. [ci skip].
  `core_ext/string/access.rb` test what we are documenting.
  Fix typo in image_tag documentation
  ...

Conflicts:
	activerecord/lib/active_record/associations/join_dependency/join_association.rb
	activerecord/lib/active_record/relation/query_methods.rb

1 files changed, 84 insertions, 99 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 52936817f8..ea2c3f233d 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -7,7 +7,7 @@ module ActiveRecord
 
     MULTI_VALUE_METHODS  = [:includes, :eager_load, :preload, :select, :group,
                             :order, :joins, :where, :having, :bind, :references,
-                            :extending]
+                            :extending, :unscope]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :from, :reordering,
                             :reverse_order, :distinct, :create_with, :uniq]
@@ -17,18 +17,14 @@ module ActiveRecord
     include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches, Explain, Delegation
 
     attr_reader :table, :klass, :loaded
-    attr_accessor :default_scoped
     alias :model :klass
     alias :loaded? :loaded
-    alias :default_scoped? :default_scoped
 
     def initialize(klass, table, values = {})
-      @klass             = klass
-      @table             = table
-      @values            = values
-      @implicit_readonly = nil
-      @loaded            = false
-      @default_scoped    = false
+      @klass  = klass
+      @table  = table
+      @values = values
+      @loaded = false
     end
 
     def initialize_copy(other)
@@ -75,11 +71,11 @@ module ActiveRecord
 
     def update_record(values, id, id_was) # :nodoc:
       substitutes, binds = substitute_values values
-      um = @klass.unscoped.where(@klass.arel_table[@klass.primary_key].eq(id_was || id)).arel.compile_update(substitutes)
-      
+      um = @klass.unscoped.where(@klass.arel_table[@klass.primary_key].eq(id_was || id)).arel.compile_update(substitutes, @klass.primary_key)
+
       @klass.connection.update(
-        um, 
-        'SQL', 
+        um,
+        'SQL',
         binds)
     end
 
@@ -94,7 +90,7 @@ module ActiveRecord
       end
 
       [substitutes, binds]
-    end 
+    end
 
     # Initializes new record from relation while maintaining the current
     # scope.
@@ -155,34 +151,58 @@ module ActiveRecord
       first || new(attributes, &block)
     end
 
-    # Finds the first record with the given attributes, or creates a record with the attributes
-    # if one is not found.
+    # Finds the first record with the given attributes, or creates a record
+    # with the attributes if one is not found:
     #
-    # ==== Examples
-    #   # Find the first user named Penélope or create a new one.
+    #   # Find the first user named "Penélope" or create a new one.
     #   User.find_or_create_by(first_name: 'Penélope')
-    #   # => <User id: 1, first_name: 'Penélope', last_name: nil>
+    #   # => #<User id: 1, first_name: "Penélope", last_name: nil>
     #
-    #   # Find the first user named Penélope or create a new one.
+    #   # Find the first user named "Penélope" or create a new one.
     #   # We already have one so the existing record will be returned.
     #   User.find_or_create_by(first_name: 'Penélope')
-    #   # => <User id: 1, first_name: 'Penélope', last_name: nil>
+    #   # => #<User id: 1, first_name: "Penélope", last_name: nil>
     #
-    #   # Find the first user named Scarlett or create a new one with a particular last name.
+    #   # Find the first user named "Scarlett" or create a new one with
+    #   # a particular last name.
     #   User.create_with(last_name: 'Johansson').find_or_create_by(first_name: 'Scarlett')
-    #   # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+    #   # => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">
     #
-    #   # Find the first user named Scarlett or create a new one with a different last name.
-    #   # We already have one so the existing record will be returned.
+    # This method accepts a block, which is passed down to +create+. The last example
+    # above can be alternatively written this way:
+    #
+    #   # Find the first user named "Scarlett" or create a new one with a
+    #   # different last name.
     #   User.find_or_create_by(first_name: 'Scarlett') do |user|
-    #     user.last_name = "O'Hara"
+    #     user.last_name = 'Johansson'
     #   end
-    #   # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+    #   # => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">
+    #
+    # This method always returns a record, but if creation was attempted and
+    # failed due to validation errors it won't be persisted, you get what
+    # +create+ returns in such situation.
+    #
+    # Please note *this method is not atomic*, it runs first a SELECT, and if
+    # there are no results an INSERT is attempted. If there are other threads
+    # or processes there is a race condition between both calls and it could
+    # be the case that you end up with two similar records.
+    #
+    # Whether that is a problem or not depends on the logic of the
+    # application, but in the particular case in which rows have a UNIQUE
+    # constraint an exception may be raised, just retry:
+    #
+    #  begin
+    #    CreditAccount.find_or_create_by(user_id: user.id)
+    #  rescue ActiveRecord::RecordNotUnique
+    #    retry
+    #  end
+    #
     def find_or_create_by(attributes, &block)
       find_by(attributes) || create(attributes, &block)
     end
 
-    # Like <tt>find_or_create_by</tt>, but calls <tt>create!</tt> so an exception is raised if the created record is invalid.
+    # Like <tt>find_or_create_by</tt>, but calls <tt>create!</tt> so an exception
+    # is raised if the created record is invalid.
     def find_or_create_by!(attributes, &block)
       find_by(attributes) || create!(attributes, &block)
     end
@@ -225,8 +245,13 @@ module ActiveRecord
     def empty?
       return @records.empty? if loaded?
 
-      c = count
-      c.respond_to?(:zero?) ? c.zero? : c.empty?
+      if limit_value == 0
+        true
+      else
+        # FIXME: This count is not compatible with #select('authors.*') or other select narrows
+        c = count
+        c.respond_to?(:zero?) ? c.zero? : c.empty?
+      end
     end
 
     # Returns true if there are any records.
@@ -291,7 +316,7 @@ module ActiveRecord
       stmt.table(table)
       stmt.key = table[primary_key]
 
-      if with_default_scope.joins_values.any?
+      if joins_values.any?
         @klass.connection.join_to_update(stmt, arel)
       else
         stmt.take(arel.limit)
@@ -416,7 +441,7 @@ module ActiveRecord
         stmt = Arel::DeleteManager.new(arel.engine)
         stmt.from(table)
 
-        if with_default_scope.joins_values.any?
+        if joins_values.any?
           @klass.connection.join_to_delete(stmt, arel, table[primary_key])
         else
           stmt.wheres = arel.constraints
@@ -490,7 +515,21 @@ module ActiveRecord
     #   User.where(name: 'Oscar').to_sql
     #   # => SELECT "users".* FROM "users"  WHERE "users"."name" = 'Oscar'
     def to_sql
-      @to_sql ||= klass.connection.to_sql(arel, bind_values.dup)
+      @to_sql ||= begin
+                    relation   = self
+                    connection = klass.connection
+                    visitor    = connection.visitor
+
+                    if eager_loading?
+                      find_with_associations { |rel| relation = rel }
+                    end
+
+                    ast   = relation.arel.ast
+                    binds = relation.bind_values.dup
+                    visitor.accept(ast) do
+                      connection.quote(*binds.shift.reverse)
+                    end
+                  end
     end
 
     # Returns a hash of where conditions.
@@ -498,12 +537,11 @@ module ActiveRecord
     #   User.where(name: 'Oscar').where_values_hash
     #   # => {name: "Oscar"}
     def where_values_hash
-      scope = with_default_scope
-      equalities = scope.where_values.grep(Arel::Nodes::Equality).find_all { |node|
+      equalities = where_values.grep(Arel::Nodes::Equality).find_all { |node|
         node.left.relation.name == table_name
       }
 
-      binds = Hash[scope.bind_values.find_all(&:first).map { |column, v| [column.name, v] }]
+      binds = Hash[bind_values.find_all(&:first).map { |column, v| [column.name, v] }]
       binds.merge!(Hash[bind_values.find_all(&:first).map { |column, v| [column.name, v] }])
 
       Hash[equalities.map { |where|
@@ -551,16 +589,6 @@ module ActiveRecord
       q.pp(self.to_a)
     end
 
-    def with_default_scope #:nodoc:
-      if default_scoped? && default_scope = klass.send(:build_default_scope)
-        default_scope = default_scope.merge(self)
-        default_scope.default_scoped = false
-        default_scope
-      else
-        self
-      end
-    end
-
     # Returns true if relation is blank.
     def blank?
       to_a.blank?
@@ -580,34 +608,24 @@ module ActiveRecord
     private
 
     def exec_queries
-      default_scoped = with_default_scope
-
-      if default_scoped.equal?(self)
-        @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, bind_values)
+      @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, bind_values)
 
-        preload = preload_values
-        preload +=  includes_values unless eager_loading?
-        preload.each do |associations|
-          ActiveRecord::Associations::Preloader.new(@records, associations).run
-        end
-
-        # @readonly_value is true only if set explicitly. @implicit_readonly is true if there
-        # are JOINS and no explicit SELECT.
-        readonly = readonly_value.nil? ? @implicit_readonly : readonly_value
-        @records.each { |record| record.readonly! } if readonly
-      else
-        @records = default_scoped.to_a
+      preload = preload_values
+      preload +=  includes_values unless eager_loading?
+      preloader = ActiveRecord::Associations::Preloader.new
+      preload.each do |associations|
+        preloader.preload @records, associations
       end
 
+      @records.each { |record| record.readonly! } if readonly_value
+
       @loaded = true
       @records
     end
 
     def references_eager_loaded_tables?
       joined_tables = arel.join_sources.map do |join|
-        if join.is_a?(Arel::Nodes::StringJoin)
-          tables_in_string(join.left)
-        else
+        unless join.is_a?(Arel::Nodes::StringJoin)
           [join.left.table_name, join.left.table_alias]
         end
       end
@@ -616,41 +634,8 @@ module ActiveRecord
 
       # always convert table names to downcase as in Oracle quoted table names are in uppercase
       joined_tables = joined_tables.flatten.compact.map { |t| t.downcase }.uniq
-      string_tables = tables_in_string(to_sql)
-
-      if (references_values - joined_tables).any?
-        true
-      elsif !ActiveRecord::Base.disable_implicit_join_references &&
-            (string_tables - joined_tables).any?
-        ActiveSupport::Deprecation.warn(
-          "It looks like you are eager loading table(s) (one of: #{string_tables.join(', ')}) " \
-          "that are referenced in a string SQL snippet. For example: \n" \
-          "\n" \
-          "    Post.includes(:comments).where(\"comments.title = 'foo'\")\n" \
-          "\n" \
-          "Currently, Active Record recognizes the table in the string, and knows to JOIN the " \
-          "comments table to the query, rather than loading comments in a separate query. " \
-          "However, doing this without writing a full-blown SQL parser is inherently flawed. " \
-          "Since we don't want to write an SQL parser, we are removing this functionality. " \
-          "From now on, you must explicitly tell Active Record when you are referencing a table " \
-          "from a string:\n" \
-          "\n" \
-          "    Post.includes(:comments).where(\"comments.title = 'foo'\").references(:comments)\n" \
-          "\n" \
-          "If you don't rely on implicit join references you can disable the feature entirely " \
-          "by setting `config.active_record.disable_implicit_join_references = true`."
-        )
-        true
-      else
-        false
-      end
-    end
 
-    def tables_in_string(string)
-      return [] if string.blank?
-      # always convert table names to downcase as in Oracle quoted table names are in uppercase
-      # ignore raw_sql_ that is used by Oracle adapter as alias for limit/offset subqueries
-      string.scan(/([a-zA-Z_][.\w]+).?\./).flatten.map{ |s| s.downcase }.uniq - ['raw_sql_']
+      (references_values - joined_tables).any?
     end
   end
 end