Use `utf8mb4` charset for internal tables if the row format `DYNAMIC` by default

The indexing issue on `utf8mb4` columns is resolved since MySQL 5.7.9.

1 files changed, 9 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index 4894fd1c08..66db4e4149 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -79,7 +79,7 @@ module ActiveRecord
 
         def internal_string_options_for_primary_key
           super.tap do |options|
-            if CHARSETS_OF_4BYTES_MAXLEN.include?(charset) && (mariadb? || version < "8.0.0")
+            if !row_format_dynamic_by_default? && CHARSETS_OF_4BYTES_MAXLEN.include?(charset)
               options[:collation] = collation.sub(/\A[^_]+/, "utf8")
             end
           end
@@ -96,6 +96,14 @@ module ActiveRecord
         private
           CHARSETS_OF_4BYTES_MAXLEN = ["utf8mb4", "utf16", "utf16le", "utf32"]
 
+          def row_format_dynamic_by_default?
+            if mariadb?
+              version >= "10.2.2"
+            else
+              version >= "5.7.9"
+            end
+          end
+
           def schema_creation
             MySQL::SchemaCreation.new(self)
           end