Fix find_by cache to work with multiple contexts

Previously it was global across contexts which would cause issues if
contexts don't generate the same queries.

Author: skipkayhil

activerecord/lib/active_record/core.rb

@@ -263,7 +263,7 @@ def self.strict_loading_violation!(owner:, reflection:) # :nodoc:
 
     module ClassMethods
       def initialize_find_by_cache # :nodoc:
-        @find_by_statement_cache = { true => Concurrent::Map.new, false => Concurrent::Map.new }
+        model_schemas.each_value(&:initialize_find_by_cache)
       end
 
       def find(*ids) # :nodoc:
@@ -402,8 +402,7 @@ def type_caster # :nodoc:
       end
 
       def cached_find_by_statement(connection, key, &block) # :nodoc:
-        cache = @find_by_statement_cache[connection.prepared_statements]
-        cache.compute_if_absent(key) { StatementCache.create(connection, &block) }
+        model_schema.cached_find_by_statement(connection, key, &block)
       end
 
       private

activerecord/lib/active_record/model_schema/schema.rb

@@ -196,6 +196,16 @@ def table_name=(value)
         @sequence_name = nil
       end
 
+      def cached_find_by_statement(connection, key, &block)
+        @find_by_statement_cache ||= { true => Concurrent::Map.new, false => Concurrent::Map.new }
+        cache = @find_by_statement_cache[connection.prepared_statements]
+        cache.compute_if_absent(key) { StatementCache.create(connection, &block) }
+      end
+
+      def initialize_find_by_cache
+        @find_by_statement_cache = { true => Concurrent::Map.new, false => Concurrent::Map.new }
+      end
+
       # Load schema information from the schema cache
       def load_schema
         return if schema_loaded?

activerecord/test/cases/core_test.rb

@@ -246,7 +246,7 @@ def attribute_for_inspect(attr_name)
   def test_find_by_cache_does_not_duplicate_entries
     Topic.initialize_find_by_cache
     using_prepared_statements = Topic.lease_connection.prepared_statements
-    topic_find_by_cache = Topic.instance_variable_get("@find_by_statement_cache")[using_prepared_statements]
+    topic_find_by_cache = Topic.model_schema.instance_variable_get("@find_by_statement_cache")[using_prepared_statements]
 
     assert_difference -> { topic_find_by_cache.size }, +1 do
       Topic.find(1)