Avoid duplicate clauses when using #or

Condenses the clauses that are common to both sides of the OR and put them outside, before the OR
This fix the current behavior where the number of conditions is exponential based on the number of times #or is used.

1 files changed, 16 insertions, 9 deletions

diff --git a/activerecord/lib/active_record/relation/where_clause.rb b/activerecord/lib/active_record/relation/where_clause.rb
index ef2bca9155..5b68c25bdd 100644
--- a/activerecord/lib/active_record/relation/where_clause.rb
+++ b/activerecord/lib/active_record/relation/where_clause.rb
@@ -15,6 +15,12 @@ module ActiveRecord
         )
       end
 
+      def -(other)
+        WhereClause.new(
+          predicates - other.predicates,
+        )
+      end
+
       def merge(other)
         WhereClause.new(
           predicates_unreferenced_by(other) + other.predicates,
@@ -26,15 +32,16 @@ module ActiveRecord
       end
 
       def or(other)
-        if empty?
-          self
-        elsif other.empty?
-          other
-        else
-          WhereClause.new(
-            [ast.or(other.ast)],
-          )
-        end
+        left = self - other
+        common = self - left
+        right = other - common
+
+        return common if left.empty? || right.empty?
+
+        or_clause = WhereClause.new(
+          [left.ast.or(right.ast)]
+        )
+        common + or_clause
       end
 
       def to_h(table_name = nil)