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

mysql-test/suite/sql_sequence/concurrent_create.result

+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CREATE SEQUENCE s2 ENGINE=InnoDB;
+connect  con1,localhost,root,,test;
+CREATE TABLE s3 LIKE s2;;
+connection default;
+CREATE SEQUENCE s4 ENGINE=InnoDB;
+SELECT * from s1 WHERE start_value IN (SELECT start_value FROM s2);
+next_not_cached_value	minimum_value	maximum_value	start_value	increment	cache_size	cycle_option	cycle_count
+1	1	9223372036854775806	1	1	1000	0	0
+connection con1;
+disconnect con1;
+connection default;
+DROP SEQUENCE s1, s2, s3, s4;
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+PREPARE stmt FROM "CREATE TABLE s2 LIKE s1";
+execute stmt;
+drop table s2;
+execute stmt;
+drop table s2;
+execute stmt;
+select * from s2;
+next_not_cached_value	minimum_value	maximum_value	start_value	increment	cache_size	cycle_option	cycle_count
+1	1	9223372036854775806	1	1	1000	0	0
+DROP SEQUENCE s1, s2;

mysql-test/suite/sql_sequence/concurrent_create.test

+--source include/have_sequence.inc
+--source include/have_innodb.inc
+
+#
+# MDEV-15149 Assorted assertion failures upon concurrent creating / querying
+# sequences (same test case)
+#
+
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CREATE SEQUENCE s2 ENGINE=InnoDB;
+
+--connect (con1,localhost,root,,test)
+--send CREATE TABLE s3 LIKE s2;
+
+--connection default
+CREATE SEQUENCE s4 ENGINE=InnoDB;
+SELECT * from s1 WHERE start_value IN (SELECT start_value FROM s2);
+
+--connection con1
+--reap
+
+# Cleanup
+--disconnect con1
+--connection default
+DROP SEQUENCE s1, s2, s3, s4;
+
+#
+# Check prepared statements
+#
+
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+PREPARE stmt FROM "CREATE TABLE s2 LIKE s1";
+execute stmt;
+drop table s2;
+execute stmt;
+drop table s2;
+execute stmt;
+select * from s2;
+DROP SEQUENCE s1, s2;
+

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 */
   }

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;
 }