1 files changed, 21 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
index 684c7042a7..56f777f3be 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -19,8 +19,19 @@ module ActiveRecord
           execute(sql, name).to_a
         end
 
+        READ_QUERY = ActiveRecord::ConnectionAdapters::AbstractAdapter.build_read_query_regexp(:begin, :select, :set, :show, :release, :savepoint) # :nodoc:
+        private_constant :READ_QUERY
+
+        def write_query?(sql) # :nodoc:
+          !READ_QUERY.match?(sql)
+        end
+
         # Executes the SQL statement in the context of this connection.
         def execute(sql, name = nil)
+          if preventing_writes? && write_query?(sql)
+            raise ActiveRecord::ReadOnlyError, "Write query attempted while in readonly mode: #{sql}"
+          end
+
           # make sure we carry over any changes to ActiveRecord::Base.default_timezone that have been
           # made since we established the connection
           @connection.query_options[:database_timezone] = ActiveRecord::Base.default_timezone
@@ -33,11 +44,19 @@ module ActiveRecord
 
           if without_prepared_statement?(binds)
             execute_and_free(sql, name) do |result|
-              ActiveRecord::Result.new(result.fields, result.to_a) if result
+              if result
+                ActiveRecord::Result.new(result.fields, result.to_a)
+              else
+                ActiveRecord::Result.new([], [])
+              end
             end
           else
             exec_stmt_and_free(sql, name, binds, cache_stmt: prepare) do |_, result|
-              ActiveRecord::Result.new(result.fields, result.to_a) if result
+              if result
+                ActiveRecord::Result.new(result.fields, result.to_a)
+              else
+                ActiveRecord::Result.new([], [])
+              end
             end
           end
         end