Always discard mysql2 multi-statement results

Same as Trilogy, using abandon_results! needs to be done on the same
original connection, and the best way to do that is inside raw_execute.

Author: jhawthorn

activerecord/lib/active_record/connection_adapters/mysql2/database_statements.rb

@@ -6,16 +6,11 @@ module Mysql2
       module DatabaseStatements
         # Returns an ActiveRecord::Result instance.
         def select_all(*, **) # :nodoc:
-          result = nil
-          with_raw_connection do |conn|
-            result = if ExplainRegistry.collect? && prepared_statements
-              unprepared_statement { super }
-            else
-              super
-            end
-            conn.abandon_results!
+          if ExplainRegistry.collect? && prepared_statements
+            unprepared_statement { super }
+          else
+            super
           end
-          result
         end
 
         def internal_exec_query(sql, name = "SQL", binds = [], prepare: false, async: false, allow_retry: false) # :nodoc:
@@ -60,7 +55,6 @@ def execute_batch(statements, name = nil)
             combine_multi_statements(statements).each do |statement|
               with_raw_connection do |conn|
                 raw_execute(statement, name)
-                conn.abandon_results!
               end
             end
           end
@@ -102,6 +96,7 @@ def raw_execute(sql, name, async: false, allow_retry: false, materialize_transac
               with_raw_connection(allow_retry: allow_retry, materialize_transactions: materialize_transactions) do |conn|
                 sync_timezone_changes(conn)
                 result = conn.query(sql)
+                conn.abandon_results!
                 verified!
                 handle_warnings(sql)
                 notification_payload[:row_count] = result&.size || 0