Prepared statements shouldn't share a cache with unprepared statements

When prepared statements are enabled, the statement cache caches the SQL
directly, including the bind parameters. If a similar query is run later
with prepared statements disabled, we need to use a separate cache
instead of trying to share the same one.

Fixes #24351

2 files changed, 16 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 86ec8000fb..c8343dd97f 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -136,7 +136,7 @@ module ActiveRecord
       end
 
       def initialize_find_by_cache # :nodoc:
-        @find_by_statement_cache = {}.extend(Mutex_m)
+        @find_by_statement_cache = { true => {}.extend(Mutex_m), false => {}.extend(Mutex_m) }
       end
 
       def inherited(child_class) # :nodoc:
@@ -280,8 +280,9 @@ module ActiveRecord
       private
 
       def cached_find_by_statement(key, &block) # :nodoc:
-        @find_by_statement_cache[key] || @find_by_statement_cache.synchronize {
-          @find_by_statement_cache[key] ||= StatementCache.create(connection, &block)
+        cache = @find_by_statement_cache[connection.prepared_statements]
+        cache[key] || cache.synchronize {
+          cache[key] ||= StatementCache.create(connection, &block)
         }
       end
 
diff --git a/activerecord/test/cases/statement_cache_test.rb b/activerecord/test/cases/statement_cache_test.rb
index a704b861cb..104226010a 100644
--- a/activerecord/test/cases/statement_cache_test.rb
+++ b/activerecord/test/cases/statement_cache_test.rb
@@ -94,5 +94,17 @@ module ActiveRecord
       additional_books = cache.execute([], Book, Book.connection)
       assert first_books != additional_books
     end
+
+    def test_unprepared_statements_dont_share_a_cache_with_prepared_statements
+      Book.create(name: "my book")
+      Book.create(name: "my other book")
+
+      book = Book.find_by(name: "my book")
+      other_book = Book.connection.unprepared_statement do
+        Book.find_by(name: "my other book")
+      end
+
+      refute_equal book, other_book
+    end
   end
 end