Arel: Implemented DB-aware NULL-safe comparison (#34451)

* Arel: Implemented DB-aware NULL-safe comparison

* Fixed where clause inversion for NULL-safe comparison

* Renaming "null_safe_eq" to "is_not_distinct_from", "null_safe_not_eq" to "is_distinct_from"

[Dmytro Shteflyuk + Rafael Mendonça França]

23 files changed, 492 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index a502713e56..e225628bae 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -125,6 +125,10 @@ module ActiveRecord
             raise ArgumentError, "Invalid argument for .where.not(), got nil."
           when Arel::Nodes::In
             Arel::Nodes::NotIn.new(node.left, node.right)
+          when Arel::Nodes::IsNotDistinctFrom
+            Arel::Nodes::IsDistinctFrom.new(node.left, node.right)
+          when Arel::Nodes::IsDistinctFrom
+            Arel::Nodes::IsNotDistinctFrom.new(node.left, node.right)
           when Arel::Nodes::Equality
             Arel::Nodes::NotEqual.new(node.left, node.right)
           when String
diff --git a/activerecord/lib/arel/nodes/equality.rb b/activerecord/lib/arel/nodes/equality.rb
index 2aa85a977e..551d56c2ff 100644
--- a/activerecord/lib/arel/nodes/equality.rb
+++ b/activerecord/lib/arel/nodes/equality.rb
@@ -7,5 +7,12 @@ module Arel # :nodoc: all
       alias :operand1 :left
       alias :operand2 :right
     end
+
+    %w{
+      IsDistinctFrom
+      IsNotDistinctFrom
+    }.each do |name|
+      const_set name, Class.new(Equality)
+    end
   end
 end
diff --git a/activerecord/lib/arel/predications.rb b/activerecord/lib/arel/predications.rb
index e83a6f162f..77502dd199 100644
--- a/activerecord/lib/arel/predications.rb
+++ b/activerecord/lib/arel/predications.rb
@@ -18,6 +18,14 @@ module Arel # :nodoc: all
       Nodes::Equality.new self, quoted_node(other)
     end
 
+    def is_not_distinct_from(other)
+      Nodes::IsNotDistinctFrom.new self, quoted_node(other)
+    end
+
+    def is_distinct_from(other)
+      Nodes::IsDistinctFrom.new self, quoted_node(other)
+    end
+
     def eq_any(others)
       grouping_any :eq, others
     end
diff --git a/activerecord/lib/arel/visitors/depth_first.rb b/activerecord/lib/arel/visitors/depth_first.rb
index 8f65d303ac..92d309453c 100644
--- a/activerecord/lib/arel/visitors/depth_first.rb
+++ b/activerecord/lib/arel/visitors/depth_first.rb
@@ -95,6 +95,8 @@ module Arel # :nodoc: all
         alias :visit_Arel_Nodes_NotEqual           :binary
         alias :visit_Arel_Nodes_NotIn              :binary
         alias :visit_Arel_Nodes_NotRegexp          :binary
+        alias :visit_Arel_Nodes_IsNotDistinctFrom  :binary
+        alias :visit_Arel_Nodes_IsDistinctFrom     :binary
         alias :visit_Arel_Nodes_Or                 :binary
         alias :visit_Arel_Nodes_OuterJoin          :binary
         alias :visit_Arel_Nodes_Regexp             :binary
diff --git a/activerecord/lib/arel/visitors/dot.rb b/activerecord/lib/arel/visitors/dot.rb
index 9054f0159b..6389c875cb 100644
--- a/activerecord/lib/arel/visitors/dot.rb
+++ b/activerecord/lib/arel/visitors/dot.rb
@@ -195,6 +195,8 @@ module Arel # :nodoc: all
         alias :visit_Arel_Nodes_JoinSource         :binary
         alias :visit_Arel_Nodes_LessThan           :binary
         alias :visit_Arel_Nodes_LessThanOrEqual    :binary
+        alias :visit_Arel_Nodes_IsNotDistinctFrom  :binary
+        alias :visit_Arel_Nodes_IsDistinctFrom     :binary
         alias :visit_Arel_Nodes_Matches            :binary
         alias :visit_Arel_Nodes_NotEqual           :binary
         alias :visit_Arel_Nodes_NotIn              :binary
diff --git a/activerecord/lib/arel/visitors/ibm_db.rb b/activerecord/lib/arel/visitors/ibm_db.rb
index 0a06aef60b..73166054da 100644
--- a/activerecord/lib/arel/visitors/ibm_db.rb
+++ b/activerecord/lib/arel/visitors/ibm_db.rb
@@ -10,6 +10,12 @@ module Arel # :nodoc: all
           collector = visit o.expr, collector
           collector << " ROWS ONLY"
         end
+
+        def is_distinct_from(o, collector)
+          collector << "DECODE("
+          collector = visit [o.left, o.right, 0, 1], collector
+          collector << ")"
+        end
     end
   end
 end
diff --git a/activerecord/lib/arel/visitors/mssql.rb b/activerecord/lib/arel/visitors/mssql.rb
index d564e19089..fdd864b40d 100644
--- a/activerecord/lib/arel/visitors/mssql.rb
+++ b/activerecord/lib/arel/visitors/mssql.rb
@@ -12,6 +12,31 @@ module Arel # :nodoc: all
 
       private
 
+        def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
+          right = o.right
+
+          if right.nil?
+            collector = visit o.left, collector
+            collector << " IS NULL"
+          else
+            collector << "EXISTS (VALUES ("
+            collector = visit o.left, collector
+            collector << ") INTERSECT VALUES ("
+            collector = visit right, collector
+            collector << "))"
+          end
+        end
+
+        def visit_Arel_Nodes_IsDistinctFrom(o, collector)
+          if o.right.nil?
+            collector = visit o.left, collector
+            collector << " IS NOT NULL"
+          else
+            collector << "NOT "
+            visit_Arel_Nodes_IsNotDistinctFrom o, collector
+          end
+        end
+
         def visit_Arel_Visitors_MSSQL_RowNumber(o, collector)
           collector << "ROW_NUMBER() OVER (ORDER BY "
           inject_join(o.children, collector, ", ") << ") as _row_num"
diff --git a/activerecord/lib/arel/visitors/mysql.rb b/activerecord/lib/arel/visitors/mysql.rb
index 4e7b2456aa..dd77cfdf66 100644
--- a/activerecord/lib/arel/visitors/mysql.rb
+++ b/activerecord/lib/arel/visitors/mysql.rb
@@ -37,6 +37,17 @@ module Arel # :nodoc: all
           collector
         end
 
+        def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
+          collector = visit o.left, collector
+          collector << " <=> "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_IsDistinctFrom(o, collector)
+          collector << "NOT "
+          visit_Arel_Nodes_IsNotDistinctFrom o, collector
+        end
+
         # In the simple case, MySQL allows us to place JOINs directly into the UPDATE
         # query. However, this does not allow for LIMIT, OFFSET and ORDER. To support
         # these, we must use a subquery.
diff --git a/activerecord/lib/arel/visitors/oracle.rb b/activerecord/lib/arel/visitors/oracle.rb
index 30a1529d46..f96bf65ee5 100644
--- a/activerecord/lib/arel/visitors/oracle.rb
+++ b/activerecord/lib/arel/visitors/oracle.rb
@@ -148,6 +148,12 @@ module Arel # :nodoc: all
         def visit_Arel_Nodes_BindParam(o, collector)
           collector.add_bind(o.value) { |i| ":a#{i}" }
         end
+
+        def is_distinct_from(o, collector)
+          collector << "DECODE("
+          collector = visit [o.left, o.right, 0, 1], collector
+          collector << ")"
+        end
     end
   end
 end
diff --git a/activerecord/lib/arel/visitors/oracle12.rb b/activerecord/lib/arel/visitors/oracle12.rb
index 7061f06087..b092aa95e0 100644
--- a/activerecord/lib/arel/visitors/oracle12.rb
+++ b/activerecord/lib/arel/visitors/oracle12.rb
@@ -56,6 +56,12 @@ module Arel # :nodoc: all
         def visit_Arel_Nodes_BindParam(o, collector)
           collector.add_bind(o.value) { |i| ":a#{i}" }
         end
+
+        def is_distinct_from(o, collector)
+          collector << "DECODE("
+          collector = visit [o.left, o.right, 0, 1], collector
+          collector << ")"
+        end
     end
   end
 end
diff --git a/activerecord/lib/arel/visitors/postgresql.rb b/activerecord/lib/arel/visitors/postgresql.rb
index c5110fa89c..920776b4dc 100644
--- a/activerecord/lib/arel/visitors/postgresql.rb
+++ b/activerecord/lib/arel/visitors/postgresql.rb
@@ -77,6 +77,18 @@ module Arel # :nodoc: all
           grouping_parentheses o, collector
         end
 
+        def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
+          collector = visit o.left, collector
+          collector << " IS NOT DISTINCT FROM "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_IsDistinctFrom(o, collector)
+          collector = visit o.left, collector
+          collector << " IS DISTINCT FROM "
+          visit o.right, collector
+        end
+
         # Used by Lateral visitor to enclose select queries in parentheses
         def grouping_parentheses(o, collector)
           if o.expr.is_a? Nodes::SelectStatement
diff --git a/activerecord/lib/arel/visitors/sqlite.rb b/activerecord/lib/arel/visitors/sqlite.rb
index cb1d2424ad..af6f7e856a 100644
--- a/activerecord/lib/arel/visitors/sqlite.rb
+++ b/activerecord/lib/arel/visitors/sqlite.rb
@@ -22,6 +22,18 @@ module Arel # :nodoc: all
         def visit_Arel_Nodes_False(o, collector)
           collector << "0"
         end
+
+        def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
+          collector = visit o.left, collector
+          collector << " IS "
+          visit o.right, collector
+        end
+
+        def visit_Arel_Nodes_IsDistinctFrom(o, collector)
+          collector = visit o.left, collector
+          collector << " IS NOT "
+          visit o.right, collector
+        end
     end
   end
 end
diff --git a/activerecord/lib/arel/visitors/to_sql.rb b/activerecord/lib/arel/visitors/to_sql.rb
index 7efd74dbc9..f9fe4404eb 100644
--- a/activerecord/lib/arel/visitors/to_sql.rb
+++ b/activerecord/lib/arel/visitors/to_sql.rb
@@ -641,6 +641,26 @@ module Arel # :nodoc: all
           end
         end
 
+        def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
+          if o.right.nil?
+            collector = visit o.left, collector
+            collector << " IS NULL"
+          else
+            collector = is_distinct_from(o, collector)
+            collector << " = 0"
+          end
+        end
+
+        def visit_Arel_Nodes_IsDistinctFrom(o, collector)
+          if o.right.nil?
+            collector = visit o.left, collector
+            collector << " IS NOT NULL"
+          else
+            collector = is_distinct_from(o, collector)
+            collector << " = 1"
+          end
+        end
+
         def visit_Arel_Nodes_NotEqual(o, collector)
           right = o.right
 
@@ -873,6 +893,19 @@ module Arel # :nodoc: all
             collector
           end
         end
+
+        def is_distinct_from(o, collector)
+          collector << "CASE WHEN "
+          collector = visit o.left, collector
+          collector << " = "
+          collector = visit o.right, collector
+          collector << " OR ("
+          collector = visit o.left, collector
+          collector << " IS NULL AND "
+          collector = visit o.right, collector
+          collector << " IS NULL)"
+          collector << " THEN 0 ELSE 1 END"
+        end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/ibm_db_test.rb b/activerecord/test/cases/arel/visitors/ibm_db_test.rb
index 7163cb34d3..2ddbec3266 100644
--- a/activerecord/test/cases/arel/visitors/ibm_db_test.rb
+++ b/activerecord/test/cases/arel/visitors/ibm_db_test.rb
@@ -29,6 +29,45 @@ module Arel
         sql = compile(stmt)
         sql.must_be_like "UPDATE \"users\" WHERE \"users\".\"id\" IN (SELECT \"users\".\"id\" FROM \"users\" FETCH FIRST 1 ROWS ONLY)"
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            DECODE("users"."name", 'Aaron Patterson', 0, 1) = 0
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 0
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 1
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/informix_test.rb b/activerecord/test/cases/arel/visitors/informix_test.rb
index b0b031cca3..b6c2dd6ae7 100644
--- a/activerecord/test/cases/arel/visitors/informix_test.rb
+++ b/activerecord/test/cases/arel/visitors/informix_test.rb
@@ -54,6 +54,45 @@ module Arel
         sql = compile(stmt)
         sql.must_be_like 'SELECT FROM "posts" INNER JOIN "comments"'
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            CASE WHEN "users"."name" = 'Aaron Patterson' OR ("users"."name" IS NULL AND 'Aaron Patterson' IS NULL) THEN 0 ELSE 1 END = 0
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            CASE WHEN "users"."first_name" = "users"."last_name" OR ("users"."first_name" IS NULL AND "users"."last_name" IS NULL) THEN 0 ELSE 1 END = 0
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            CASE WHEN "users"."first_name" = "users"."last_name" OR ("users"."first_name" IS NULL AND "users"."last_name" IS NULL) THEN 0 ELSE 1 END = 1
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/mssql_test.rb b/activerecord/test/cases/arel/visitors/mssql_test.rb
index 340376c3d6..74f34b4dad 100644
--- a/activerecord/test/cases/arel/visitors/mssql_test.rb
+++ b/activerecord/test/cases/arel/visitors/mssql_test.rb
@@ -94,6 +94,45 @@ module Arel
         sql = compile(stmt)
         sql.must_be_like "SELECT COUNT(1) as count_id FROM (SELECT _t.* FROM (SELECT ROW_NUMBER() OVER (ORDER BY ) as _row_num) as _t WHERE _row_num BETWEEN 1 AND 10) AS subquery"
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            EXISTS (VALUES ("users"."name") INTERSECT VALUES ('Aaron Patterson'))
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            EXISTS (VALUES ("users"."first_name") INTERSECT VALUES ("users"."last_name"))
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            NOT EXISTS (VALUES ("users"."first_name") INTERSECT VALUES ("users"."last_name"))
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/mysql_test.rb b/activerecord/test/cases/arel/visitors/mysql_test.rb
index dae98b0583..5f37587957 100644
--- a/activerecord/test/cases/arel/visitors/mysql_test.rb
+++ b/activerecord/test/cases/arel/visitors/mysql_test.rb
@@ -65,6 +65,45 @@ module Arel
           }
         end
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            "users"."name" <=> 'Aaron Patterson'
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            "users"."first_name" <=> "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" <=> NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            NOT "users"."first_name" <=> "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ NOT "users"."name" <=> NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/oracle12_test.rb b/activerecord/test/cases/arel/visitors/oracle12_test.rb
index 83a2ee36ca..4ce5cab4db 100644
--- a/activerecord/test/cases/arel/visitors/oracle12_test.rb
+++ b/activerecord/test/cases/arel/visitors/oracle12_test.rb
@@ -56,6 +56,45 @@ module Arel
           }
         end
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            DECODE("users"."name", 'Aaron Patterson', 0, 1) = 0
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 0
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 1
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/oracle_test.rb b/activerecord/test/cases/arel/visitors/oracle_test.rb
index e1dfe40cf9..893edc7f74 100644
--- a/activerecord/test/cases/arel/visitors/oracle_test.rb
+++ b/activerecord/test/cases/arel/visitors/oracle_test.rb
@@ -192,6 +192,45 @@ module Arel
           }
         end
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            DECODE("users"."name", 'Aaron Patterson', 0, 1) = 0
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 0
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            DECODE("users"."first_name", "users"."last_name", 0, 1) = 1
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/postgres_test.rb b/activerecord/test/cases/arel/visitors/postgres_test.rb
index f7f2c76b6f..0f9efb20b4 100644
--- a/activerecord/test/cases/arel/visitors/postgres_test.rb
+++ b/activerecord/test/cases/arel/visitors/postgres_test.rb
@@ -276,6 +276,45 @@ module Arel
           }
         end
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            "users"."name" IS NOT DISTINCT FROM 'Aaron Patterson'
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            "users"."first_name" IS NOT DISTINCT FROM "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT DISTINCT FROM NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            "users"."first_name" IS DISTINCT FROM "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS DISTINCT FROM NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/sqlite_test.rb b/activerecord/test/cases/arel/visitors/sqlite_test.rb
index 6650b6ff3a..ee4e07a675 100644
--- a/activerecord/test/cases/arel/visitors/sqlite_test.rb
+++ b/activerecord/test/cases/arel/visitors/sqlite_test.rb
@@ -6,7 +6,11 @@ module Arel
   module Visitors
     class SqliteTest < Arel::Spec
       before do
-        @visitor = SQLite.new Table.engine.connection_pool
+        @visitor = SQLite.new Table.engine.connection
+      end
+
+      def compile(node)
+        @visitor.accept(node, Collectors::SQLString.new).value
       end
 
       it "defaults limit to -1" do
@@ -27,6 +31,45 @@ module Arel
         node = Nodes::False.new()
         assert_equal "0", @visitor.accept(node, Collectors::SQLString.new).value
       end
+
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            "users"."name" IS 'Aaron Patterson'
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            "users"."first_name" IS "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            "users"."first_name" IS NOT "users"."last_name"
+          }
+        end
+
+        it "should handle nil" do
+          @table = Table.new(:users)
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/arel/visitors/to_sql_test.rb b/activerecord/test/cases/arel/visitors/to_sql_test.rb
index 680c26a9ab..4bfa799a96 100644
--- a/activerecord/test/cases/arel/visitors/to_sql_test.rb
+++ b/activerecord/test/cases/arel/visitors/to_sql_test.rb
@@ -155,6 +155,43 @@ module Arel
         end
       end
 
+      describe "Nodes::IsNotDistinctFrom" do
+        it "should construct a valid generic SQL statement" do
+          test = Table.new(:users)[:name].is_not_distinct_from "Aaron Patterson"
+          compile(test).must_be_like %{
+            CASE WHEN "users"."name" = 'Aaron Patterson' OR ("users"."name" IS NULL AND 'Aaron Patterson' IS NULL) THEN 0 ELSE 1 END = 0
+          }
+        end
+
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_not_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            CASE WHEN "users"."first_name" = "users"."last_name" OR ("users"."first_name" IS NULL AND "users"."last_name" IS NULL) THEN 0 ELSE 1 END = 0
+          }
+        end
+
+        it "should handle nil" do
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsNotDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NULL }
+        end
+      end
+
+      describe "Nodes::IsDistinctFrom" do
+        it "should handle column names on both sides" do
+          test = Table.new(:users)[:first_name].is_distinct_from Table.new(:users)[:last_name]
+          compile(test).must_be_like %{
+            CASE WHEN "users"."first_name" = "users"."last_name" OR ("users"."first_name" IS NULL AND "users"."last_name" IS NULL) THEN 0 ELSE 1 END = 1
+          }
+        end
+
+        it "should handle nil" do
+          val = Nodes.build_quoted(nil, @table[:active])
+          sql = compile Nodes::IsDistinctFrom.new(@table[:name], val)
+          sql.must_be_like %{ "users"."name" IS NOT NULL }
+        end
+      end
+
       it "should visit string subclass" do
         [
           Class.new(String).new(":'("),
diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index 8703d238a0..0b06cec40b 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -92,12 +92,16 @@ class ActiveRecord::Relation
       original = WhereClause.new([
         table["id"].in([1, 2, 3]),
         table["id"].eq(1),
+        table["id"].is_not_distinct_from(1),
+        table["id"].is_distinct_from(2),
         "sql literal",
         random_object
       ])
       expected = WhereClause.new([
         table["id"].not_in([1, 2, 3]),
         table["id"].not_eq(1),
+        table["id"].is_distinct_from(1),
+        table["id"].is_not_distinct_from(2),
         Arel::Nodes::Not.new(Arel::Nodes::SqlLiteral.new("sql literal")),
         Arel::Nodes::Not.new(random_object)
       ])