Make uniqueness validations correctly handle nil values

Previously, the uniqueness validations did not work correctly for
nil values, since they checked if there were other rows where
(column IS NULL).  However, in SQL, NULL = NULL is not true, and
multiple rows are allowed to have NULL values in a column with a
unique constraint.  So skip the uniqueness check if the value is
nil.

If you have a UNIQUE NOT NULL column, you should have a separate
presence check to check for the nil values.

CHANGELOG

@@ -1,5 +1,7 @@
 === HEAD
 
+* Make uniqueness validations correctly handle nil values (jeremyevans)
+
 * Add ConnectionPool#pool_type to get the type of connection pool in use (jeremyevans)
 
 * Explicitly mark primary keys as NOT NULL on SQLite (jeremyevans)

lib/sequel/plugins/validation_class_methods.rb

@@ -385,6 +385,7 @@ def validates_uniqueness_of(*atts)
             error_field = a
             a = Array(a)
             v = Array(v)
+            next if v.empty? || !v.all?
             ds = o.class.filter(a.zip(v))
             num_dups = ds.count
             allow = if num_dups == 0

lib/sequel/plugins/validation_helpers.rb

@@ -224,7 +224,9 @@ def validates_unique(*atts)
             ds = if where
               where.call(model.dataset, self, arr)
             else
-              model.where(arr.map{|x| [x, send(x)]})
+              vals = arr.map{|x| send(x)}
+              next unless vals.all?
+              model.where(arr.zip(vals))
             end
             ds = yield(ds) if block_given?
             ds = ds.exclude(pk_hash) unless new?

spec/extensions/validation_class_methods_spec.rb

@@ -578,7 +578,7 @@ def dont_skip; true; end
   specify "should validate uniqueness_of with allow_missing => true" do
     @c.validates_uniqueness_of :value, :allow_missing => true
     @m.should be_valid
-    @m.value = nil
+    @m.value = 1
     @m.should_not be_valid
   end
 end
@@ -858,6 +858,12 @@ class ::User < Sequel::Model
     @user = User.new(:username => "0records", :password => "anothertest")
     @user.should be_valid
     @user.errors.full_messages.should == []
+
+    User.db.sqls
+    @user = User.new(:password => "anothertest")
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    User.db.sqls.should == []
   end
 
   it "should validate the uniqueness of multiple columns" do
@@ -907,6 +913,18 @@ class ::User < Sequel::Model
     @user = User.new(:username => "0records", :password => "anothertest")
     @user.should be_valid
     @user.errors.full_messages.should == []
+
+    User.db.sqls
+    @user = User.new(:password => "anothertest")
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    @user = User.new(:username => "0records")
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    @user = User.new
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    User.db.sqls.should == []
   end
 
   it "should have a validates block that contains multiple validations" do

spec/extensions/validation_helpers_spec.rb

@@ -331,6 +331,11 @@ def validate
     @user = @c.load(:id=>3, :username => "0records", :password => "anothertest")
     @user.should be_valid
 
+    MODEL_DB.sqls
+    @user = @c.new(:password => "anothertest")
+    @user.should be_valid
+    MODEL_DB.sqls.should == []
+
     @user = @c.new(:username => "1record", :password => "anothertest")
     @user.should_not be_valid
     @user.errors.full_messages.should == ['username is already taken']
@@ -369,6 +374,18 @@ def validate
     @user = @c.load(:id=>3, :username => "0records", :password => "anothertest")
     @user.should be_valid
 
+    MODEL_DB.sqls
+    @user = @c.new(:password => "anothertest")
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    @user = @c.new(:username => "0records")
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    @user = @c.new
+    @user.should be_valid
+    @user.errors.full_messages.should == []
+    MODEL_DB.sqls.should == []
+
     @user = @c.new(:username => "1record", :password => "anothertest")
     @user.should_not be_valid
     @user.errors.full_messages.should == ['username and password is already taken']