MDEV-19273: Server crash in MDL_ticket::has_stronger_or_equal_type or Assertion `thd->mdl_context.is_lock_owner(MDL_key::TABLE, table->db.str, table->table_name.str, MDL_SHARED)' failed in mysql_rm_table_no_locksbb-10.3-MDEV-19273

Early report error in case of DROP SEQUENCE <non-sequence>

Do not use error variable for other purposes except error.

1 files changed, 44 insertions, 12 deletions

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 96d270b25ff..55cc33b4680 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -2314,8 +2314,11 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
   {
     bool is_trans= 0;
     bool table_creation_was_logged= 0;
+    bool real_table= FALSE;
     LEX_CSTRING db= table->db;
     handlerton *table_type= 0;
+    // reset error state for this table
+    error= 0;
 
     DBUG_PRINT("table", ("table_l: '%s'.'%s'  table: %p  s: %p",
                          table->db.str, table->table_name.str,  table->table,
@@ -2331,9 +2334,35 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
                   thd->find_temporary_table(table) &&
                   table->mdl_request.ticket != NULL));
 
-    if (table->open_type == OT_BASE_ONLY || !is_temporary_table(table) ||
-        (drop_sequence && table->table->s->table_type != TABLE_TYPE_SEQUENCE))
+    if (table->open_type == OT_BASE_ONLY || !is_temporary_table(table))
+      real_table= TRUE;
+    else if (drop_sequence &&
+            table->table->s->table_type != TABLE_TYPE_SEQUENCE)
+    {
+      was_table= (table->table->s->table_type == TABLE_TYPE_NORMAL);
+      was_view= (table->table->s->table_type == TABLE_TYPE_VIEW);
+      if (if_exists)
+      {
+        char buff[FN_REFLEN];
+        String tbl_name(buff, sizeof(buff), system_charset_info);
+        tbl_name.length(0);
+        tbl_name.append(&db);
+        tbl_name.append('.');
+        tbl_name.append(&table->table_name);
+        push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                            ER_NOT_SEQUENCE2, ER_THD(thd, ER_NOT_SEQUENCE2),
+                            tbl_name.c_ptr_safe());
+
+        /*
+          Our job is done here. This statement was added to avoid executing
+          unnecessary code farther below which in some strange corner cases
+          caused the server to crash (see MDEV-17896).
+        */
+        goto log_query;
+      }
       error= 1;
+      goto non_critical_err;
+    }
     else
     {
       table_creation_was_logged= table->table->s->table_creation_was_logged;
@@ -2342,29 +2371,28 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
         error= 1;
         goto err;
       }
-      error= 0;
       table->table= 0;
     }
 
-    if ((drop_temporary && if_exists) || !error)
+    if ((drop_temporary && if_exists) || !real_table)
     {
       /*
         This handles the case of temporary tables. We have the following cases:
 
           . "DROP TEMPORARY" was executed and a temporary table was affected
-          (i.e. drop_temporary && !error) or the if_exists was specified (i.e.
-          drop_temporary && if_exists).
+          (i.e. drop_temporary && !real_table) or the
+          if_exists was specified (i.e. drop_temporary && if_exists).
 
           . "DROP" was executed but a temporary table was affected (.i.e
-          !error).
+          !real_table).
       */
       if (!dont_log_query && table_creation_was_logged)
       {
         /*
-          If there is an error, we don't know the type of the engine
+          If there is an real_table, we don't know the type of the engine
           at this point. So, we keep it in the trx-cache.
         */
-        is_trans= error ? TRUE : is_trans;
+        is_trans= real_table ? TRUE : is_trans;
         if (is_trans)
           trans_tmp_table_deleted= TRUE;
         else
@@ -2391,7 +2419,7 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
         is no need to proceed with the code that tries to drop a regular
         table.
       */
-      if (!error) continue;
+      if (!real_table) continue;
     }
     else if (!drop_temporary)
     {
@@ -2407,7 +2435,6 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
                                         reg_ext, 0);
     }
     DEBUG_SYNC(thd, "rm_table_no_locks_before_delete_table");
-    error= 0;
     if (drop_temporary ||
         (ha_table_exists(thd, &db, &alias, &table_type, &is_sequence) == 0 &&
          table_type == 0) ||
@@ -2447,6 +2474,11 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
       {
         non_tmp_error = (drop_temporary ? non_tmp_error : TRUE);
         error= 1;
+        /*
+          non critical error (only for this table), so we continue.
+          Next we write it to wrong_tables and continue this loop
+          The same as "goto non_critical_err".
+        */
       }
     }
     else
@@ -2540,7 +2572,7 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
       }
       non_tmp_error|= MY_TEST(error);
     }
-
+non_critical_err:
     if (error)
     {
       if (wrong_tables.length())