MDEV-15149 Assert upon concurrent creating / querying sequences

Problem was that sequence_insert closed and reopened the like table
without proper locking.  Fixed by ensuring that the like table is
not reopened in sequence_insert

2 files changed, 5 insertions, 0 deletions

diff --git a/sql/sql_sequence.cc b/sql/sql_sequence.cc
index cc0691f92cf..3ef1e668667 100644
--- a/sql/sql_sequence.cc
+++ b/sql/sql_sequence.cc
@@ -283,6 +283,7 @@ bool sequence_insert(THD *thd, LEX *lex, TABLE_LIST *table_list)
   Reprepare_observer *save_reprepare_observer;
   sequence_definition *seq= lex->create_info.seq_create_info;
   bool temporary_table= table_list->table != 0;
+  TABLE_LIST *org_next_global= table_list->next_global;
   DBUG_ENTER("sequence_insert");
 
   /* If not temporary table */
@@ -290,6 +291,7 @@ bool sequence_insert(THD *thd, LEX *lex, TABLE_LIST *table_list)
   {
     /* Table was locked as part of create table. Free it but keep MDL locks */
     close_thread_tables(thd);
+    table_list->next_global= 0;                 // Close LIKE TABLE
     table_list->lock_type= TL_WRITE_DEFAULT;
     table_list->updating=  1;
     /*
@@ -312,6 +314,7 @@ bool sequence_insert(THD *thd, LEX *lex, TABLE_LIST *table_list)
     table_list->open_strategy= save_open_strategy;
     thd->open_options&= ~HA_OPEN_FOR_CREATE;
     thd->m_reprepare_observer= save_reprepare_observer;
+    table_list->next_global= org_next_global;
     if (error)
       DBUG_RETURN(TRUE); /* purify inspected */
   }
diff --git a/sql/table_cache.cc b/sql/table_cache.cc
index 18ea7f83964..e524e0995e2 100644
--- a/sql/table_cache.cc
+++ b/sql/table_cache.cc
@@ -460,6 +460,7 @@ static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
 void tc_release_table(TABLE *table)
 {
   uint32 i= table->instance;
+  DBUG_ENTER("tc_release_table");
   DBUG_ASSERT(table->in_use);
   DBUG_ASSERT(table->file);
 
@@ -478,6 +479,7 @@ void tc_release_table(TABLE *table)
     tc[i].free_tables.push_back(table);
     mysql_mutex_unlock(&tc[i].LOCK_table_cache);
   }
+  DBUG_VOID_RETURN;
 }