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, 33 insertions, 0 deletions

diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index f3a81f3c70..42cf35ac9c 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -181,6 +181,39 @@ class ActiveRecord::Relation
       assert_equal WhereClause.empty, WhereClause.empty.or(where_clause)
     end
 
+    test "or places common conditions before the OR" do
+      wcs = (0..6).map do |i|
+        WhereClause.new([table["col_#{i}"].eq(bind_param(i))])
+      end
+
+      actual = wcs[0]
+      expected = wcs[0]
+
+      actual = (actual + wcs[1]).or(actual + wcs[2])
+      expected = expected + wcs[1].or(wcs[2])
+
+      actual = (actual + wcs[3] + wcs[4]).or(actual + wcs[5] + wcs[6])
+      expected = expected + (wcs[3] + wcs[4]).or(wcs[5] + wcs[6])
+
+      assert_equal expected, actual
+    end
+
+    test "or will use common conditions only if one side only has common conditions" do
+      common = WhereClause.new(
+        [table["id"].eq(bind_param(1)), "foo = bar"]
+      )
+
+      extra = WhereClause.new([table["extra"].eq(bind_param("pluto"))])
+
+      actual_extra_only_on_left = (common + extra).or(common)
+      actual_extra_only_on_right = (common).or(common + extra)
+
+      expected = common
+
+      assert_equal expected, actual_extra_only_on_left
+      assert_equal expected, actual_extra_only_on_right
+    end
+
     private
 
       def table