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Count returns 0 without querying if parent is not saved

Patches `CollectionAssociation#count` to return 0 without querying
if the parent record is new. Consider the following code:

    class Account
      has_many :dossiers
    end

    class Dossier
      belongs_to :account
    end

    a = Account.new
    a.dossiers.build

    # before patch
    a.dossiers.count
    # SELECT COUNT(*) FROM "dossiers" WHERE "dossiers"."account_id" IS NULL
    # => 0

    # after
    a.dosiers.count # fires without sql query
    # => 0

Fixes #1856.
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1 parent e4e84fe commit aa202adf6c78468c8e03efd11d84b71478de7b03 Francesco Rodriguez committed
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17 activerecord/CHANGELOG.md
@@ -1,5 +1,22 @@
## Rails 4.0.0 (unreleased) ##
+* `CollectionAssociation#count` returns 0 without querying if the
+ parent record is new.
+
+ Before:
+
+ person.pets
+ # SELECT COUNT(*) FROM "pets" WHERE "pets"."person_id" IS NULL
+ # => 0
+
+ After:
+
+ person.pets
+ # fires without sql query
+ # => 0
+
+ *Francesco Rodriguez*
+
* Fix `reset_counters` crashing on `has_many :through` associations.
Fix #7822.
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2 activerecord/lib/active_record/associations/collection_association.rb
@@ -174,6 +174,8 @@ def sum(*args)
# association, it will be used for the query. Otherwise, construct options and pass them with
# scope to the target class's +count+.
def count(column_name = nil, count_options = {})
+ return 0 if owner.new_record?
+
column_name, count_options = nil, column_name if column_name.is_a?(Hash)
if options[:counter_sql] || options[:finder_sql]
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6 activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -799,6 +799,12 @@ def test_count_with_counter_sql
assert_equal 1, developer.projects.count
end
+ def test_counting_should_not_fire_sql_if_parent_is_unsaved
+ assert_no_queries do
+ assert_equal 0, Developer.new.projects.count
+ end
+ end
+
unless current_adapter?(:PostgreSQLAdapter)
def test_count_with_finder_sql
assert_equal 3, projects(:active_record).developers_with_finder_sql.count
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6 activerecord/test/cases/associations/has_many_associations_test.rb
@@ -262,6 +262,12 @@ def test_counting_with_association_limit
assert_equal firm.limited_clients.length, firm.limited_clients.count
end
+ def test_counting_should_not_fire_sql_if_parent_is_unsaved
+ assert_no_queries do
+ assert_equal 0, Person.new.readers.count
+ end
+ end
+
def test_finding
assert_equal 2, Firm.all.merge!(:order => "id").first.clients.length
end
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6 activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -767,6 +767,12 @@ def test_count_has_many_through_with_named_scope
assert_equal 1, authors(:mary).categories.general.count
end
+ def test_counting_should_not_fire_sql_if_parent_is_unsaved
+ assert_no_queries do
+ assert_equal 0, Person.new.posts.count
+ end
+ end
+
def test_has_many_through_belongs_to_should_update_when_the_through_foreign_key_changes
post = posts(:eager_other)

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