MDEV-10506 Protocol::end_statement(): Assertion `0' failed upon ALTER TABLE

thd->clear_error() destroyed already existing error status

1 files changed, 2 insertions, 1 deletions

diff --git a/storage/myisam/ha_myisam.cc b/storage/myisam/ha_myisam.cc
index a2e62d8ae1e..784da17d790 100644
--- a/storage/myisam/ha_myisam.cc
+++ b/storage/myisam/ha_myisam.cc
@@ -1433,6 +1433,7 @@ int ha_myisam::enable_indexes(uint mode)
   else if (mode == HA_KEY_SWITCH_NONUNIQ_SAVE)
   {
     THD *thd= table->in_use;
+    int was_error= thd->is_error();
     HA_CHECK &param= *(HA_CHECK*) thd->alloc(sizeof(param));
     const char *save_proc_info=thd->proc_info;
 
@@ -1475,7 +1476,7 @@ int ha_myisam::enable_indexes(uint mode)
         might have been set by the first repair. They can still be seen
         with SHOW WARNINGS then.
       */
-      if (! error)
+      if (! error && ! was_error)
         thd->clear_error();
     }
     info(HA_STATUS_CONST);