Refactor `build_relation` in the uniqueness validator to avoid low level predicate construction

1 files changed, 12 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 346d4b067a..0d2d66f919 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -504,15 +504,17 @@ module ActiveRecord
         @connection
       end
 
-      def case_sensitive_comparison(table, attribute, column, value) # :nodoc:
-        table[attribute].eq(value)
+      def case_sensitive_comparison(attribute, value) # :nodoc:
+        attribute.eq(value)
       end
 
-      def case_insensitive_comparison(table, attribute, column, value) # :nodoc:
+      def case_insensitive_comparison(attribute, value) # :nodoc:
+        column = column_for_attribute(attribute)
+
         if can_perform_case_insensitive_comparison_for?(column)
-          table[attribute].lower.eq(table.lower(value))
+          attribute.lower.eq(attribute.relation.lower(value))
         else
-          table[attribute].eq(value)
+          attribute.eq(value)
         end
       end
 
@@ -659,6 +661,11 @@ module ActiveRecord
             raise(ActiveRecordError, "No such column: #{table_name}.#{column_name}")
         end
 
+        def column_for_attribute(attribute)
+          table_name = attribute.relation.name
+          schema_cache.columns_hash(table_name)[attribute.name.to_s]
+        end
+
         def collector
           if prepared_statements
             Arel::Collectors::Composite.new(