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]

1 files changed, 11 insertions, 0 deletions

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.