Added support for using limits in eager loads that involve has_many and has_and_belongs_to_many associations
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2675 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
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@ -1,3 +1,7 @@
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*1.12.1*
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* Added support for using limits in eager loads that involve has_many and has_and_belongs_to_many associations
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*1.12.0* (October 16th, 2005)
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* Update/clean up documentation (rdoc)
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@ -167,9 +167,14 @@ module ActiveRecord
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# the number of queries. The database still needs to send all the data to Active Record and it still needs to be processed. So its no
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# catch-all for performance problems, but its a great way to cut down on the number of queries in a situation as the one described above.
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#
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# Please note that because eager loading is fetching both models and associations in the same grab, it doesn't make sense to use the
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# :limit and :offset options on has_many and has_and_belongs_to_many associations and an ConfigurationError exception will be raised
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# if attempted. It does, however, work just fine with has_one and belongs_to associations.
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# Please note that limited eager loading with has_many and has_and_belongs_to_many associations is not compatible with describing conditions
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# on these eager tables. This will work:
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#
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# Post.find(:all, :include => :comments, :conditions => "posts.title = 'magic forest'", :limit => 2)
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#
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# ...but this will not (and an ArgumentError will be raised):
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#
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# Post.find(:all, :include => :comments, :conditions => "comments.body like 'Normal%'", :limit => 2)
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#
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# Also have in mind that since the eager loading is pulling from multiple tables, you'll have to disambiguate any column references
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# in both conditions and orders. So :order => "posts.id DESC" will work while :order => "id DESC" will not. This may require that
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@ -766,7 +771,6 @@ module ActiveRecord
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reflections = reflect_on_included_associations(options[:include])
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guard_against_missing_reflections(reflections, options)
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guard_against_unlimitable_reflections(reflections, options)
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schema_abbreviations = generate_schema_abbreviations(reflections)
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primary_key_table = generate_primary_key_table(reflections, schema_abbreviations)
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@ -867,24 +871,61 @@ module ActiveRecord
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sql = "SELECT #{column_aliases(schema_abbreviations)} FROM #{table_name} "
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sql << reflections.collect { |reflection| association_join(reflection) }.to_s
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sql << "#{options[:joins]} " if options[:joins]
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add_conditions!(sql, options[:conditions])
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add_sti_conditions!(sql, reflections)
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add_limited_ids_condition!(sql, options) if !using_limitable_reflections?(reflections) && options[:limit]
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sql << "ORDER BY #{options[:order]} " if options[:order]
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add_limit!(sql, options) if using_limitable_reflections?(reflections)
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return sanitize_sql(sql)
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end
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def add_limited_ids_condition!(sql, options)
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unless (id_list = select_limited_ids_list(options)).empty?
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sql << "#{condition_word(sql)} #{table_name}.#{primary_key} IN (#{id_list}) "
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end
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end
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def select_limited_ids_list(options)
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connection.select_values(
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construct_finder_sql_for_association_limiting(options),
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"#{name} Load IDs For Limited Eager Loading"
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).collect { |id| "'#{id}'" }.join(", ")
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end
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def construct_finder_sql_for_association_limiting(options)
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raise(ArgumentError, "Limited eager loads and conditions on the eager tables is incompatible") if include_eager_conditions?(options)
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sql = "SELECT #{primary_key} FROM #{table_name} "
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add_conditions!(sql, options[:conditions])
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sql << "ORDER BY #{options[:order]} " if options[:order]
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add_limit!(sql, options)
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return sanitize_sql(sql)
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end
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def include_eager_conditions?(options)
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return false unless options[:conditions]
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options[:conditions].scan(/ ([^.]+)\.[^.]+ /).flatten.any? do |condition_table_name|
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condition_table_name != table_name
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end
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end
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def using_limitable_reflections?(reflections)
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reflections.reject { |r| [ :belongs_to, :has_one ].include?(r.macro) }.length.zero?
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end
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def add_sti_conditions!(sql, reflections)
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sti_sql = ""
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reflections.each do |reflection|
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sti_sql << " AND #{reflection.klass.send(:type_condition)}" unless reflection.klass.descends_from_active_record?
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sti_conditions = reflections.collect do |reflection|
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reflection.klass.send(:type_condition) unless reflection.klass.descends_from_active_record?
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end.compact
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unless sti_conditions.empty?
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sql << condition_word(sql) + sti_conditions.join(" AND ")
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end
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sti_sql.sub!(/AND/, "WHERE") unless sql =~ /where/i
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sql << sti_sql
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end
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def column_aliases(schema_abbreviations)
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@ -933,6 +974,10 @@ module ActiveRecord
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end
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return record
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end
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def condition_word(sql)
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sql =~ /where/i ? " AND " : "WHERE "
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end
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end
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end
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@ -95,8 +95,35 @@ class EagerAssociationTest < Test::Unit::TestCase
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assert_equal [], posts
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end
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def test_eager_association_raise_on_limit
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assert_raises(ActiveRecord::ConfigurationError) { Post.find(:all, :include => [:author, :comments], :limit => 1) }
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def test_eager_with_has_many_and_limit
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posts = Post.find(:all, :include => [ :author, :comments ], :limit => 2)
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assert_equal 2, posts.size
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assert_equal 3, posts.inject(0) { |sum, post| sum += post.comments.size }
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end
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def test_eager_with_has_many_and_limit_with_no_results
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posts = Post.find(:all, :include => [ :author, :comments ], :limit => 2, :conditions => "posts.title = 'magic forest'")
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assert_equal 0, posts.size
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end
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def test_eager_with_has_and_belongs_to_many_and_limit
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posts = Post.find(:all, :include => :categories, :order => "posts.id", :limit => 3)
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assert_equal 3, posts.size
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assert_equal 2, posts[0].categories.size
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assert_equal 1, posts[1].categories.size
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assert_equal 0, posts[2].categories.size
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assert posts[0].categories.include?(categories(:technology))
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assert posts[1].categories.include?(categories(:general))
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end
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def test_eager_with_has_many_and_limit_and_conditions_on_the_eagers
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assert_raises(ArgumentError) do
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posts = authors(:david).posts.find(:all,
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:include => :comments,
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:conditions => "comments.body like 'Normal%' OR comments.type = 'SpecialComment'",
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:limit => 2
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)
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end
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end
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def test_eager_association_loading_with_habtm
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