MDEV-8260 : Issues related to concurrent CTAS

* Wait for aborted thd (victim) to release MDL locks
* Skip aborting an already aborted thd
* Defer setting OK status in case of CTAS
* Minor cosmetic changes
* Added a test case

mysql-test/suite/galera/r/galera_concurrent_ctas.result

+# End of test

mysql-test/suite/galera/t/galera_concurrent_ctas.test

+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+--write_file $MYSQLTEST_VARDIR/tmp/galera_concurrent.sql
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+DROP table t1;
+CREATE table t1 as SELECT SLEEP(0);
+CREATE table t2 as SELECT SLEEP(0);
+CREATE table t3 as SELECT SLEEP(0);
+CREATE table t4 as SELECT SLEEP(0);
+CREATE table t5 as SELECT SLEEP(0);
+CREATE table t6 as SELECT SLEEP(0);
+CREATE table t7 as SELECT SLEEP(0);
+CREATE table t8 as SELECT SLEEP(0);
+CREATE table t9 as SELECT SLEEP(0);
+DROP table t1;
+DROP table t2;
+DROP table t3;
+DROP table t4;
+DROP table t5;
+DROP table t6;
+DROP table t7;
+DROP table t8;
+DROP table t9;
+EOF
+
+let $run=10;
+
+while($run)
+{
+  --error 0,1
+  exec $MYSQL --user=root --host=127.0.0.1 --port=$NODE_MYPORT_1 test
+         < $MYSQLTEST_VARDIR/tmp/galera_concurrent.sql &
+       $MYSQL --user=root --host=127.0.0.1 --port=$NODE_MYPORT_2 test
+         < $MYSQLTEST_VARDIR/tmp/galera_concurrent.sql;
+  dec $run;
+}
+
+--remove_file $MYSQLTEST_VARDIR/tmp/galera_concurrent.sql
+
+--source include/galera_end.inc
+--echo # End of test
+

sql/mdl.cc

@@ -1199,6 +1199,13 @@ MDL_wait::timed_wait(THD *thd, struct timespec *abs_timeout,
   while (!m_wait_status && !thd->killed &&
          wait_result != ETIMEDOUT && wait_result != ETIME)
   {
+#ifdef WITH_WSREP
+    if (wsrep_thd_is_BF(thd, true))
+    {
+      wait_result= mysql_cond_wait(&m_COND_wait_status, &m_LOCK_wait_status);
+    }
+    else
+#endif
     wait_result= mysql_cond_timedwait(&m_COND_wait_status, &m_LOCK_wait_status,
                                       abs_timeout);
   }
@@ -1283,12 +1290,15 @@ void MDL_lock::Ticket_list::add_ticket(MDL_ticket *ticket)
         WSREP_DEBUG("MDL add_ticket inserted before: %lu %s", 
                     wsrep_thd_thread_id(waiting->get_ctx()->get_thd()), 
                     wsrep_thd_query(waiting->get_ctx()->get_thd()));
+        /* Insert the ticket before the first non-BF waiting thd. */
         m_list.insert_after(prev, ticket);
         added= true;
       }
       prev= waiting;
     }
-    if (!added)   m_list.push_back(ticket);
+
+    /* Otherwise, insert the ticket at the back of the waiting list. */
+    if (!added) m_list.push_back(ticket);
 
     while ((granted= itg++))
     {

sql/sql_class.h

@@ -3486,6 +3486,8 @@ class select_insert :public select_result_interceptor {
   virtual void store_values(List<Item> &values);
   virtual bool can_rollback_data() { return 0; }
   void send_error(uint errcode,const char *err);
+  bool prepare_eof();
+  bool send_ok_packet();
   bool send_eof();
   virtual void abort_result_set();
   /* not implemented: select_insert is never re-used in prepared statements */

sql/sql_insert.cc

@@ -3650,14 +3650,14 @@ void select_insert::send_error(uint errcode,const char *err)
 }
 
 
-bool select_insert::send_eof()
+bool select_insert::prepare_eof()
 {
   int error;
   bool const trans_table= table->file->has_transactions();
-  ulonglong id, row_count;
   bool changed;
   killed_state killed_status= thd->killed;
-  DBUG_ENTER("select_insert::send_eof");
+
+  DBUG_ENTER("select_insert::prepare_eof");
   DBUG_PRINT("enter", ("trans_table=%d, table_type='%s'",
                        trans_table, table->file->table_type()));
 
@@ -3699,11 +3699,10 @@ bool select_insert::send_eof()
   */
 #ifdef WITH_WSREP
   if ((WSREP_EMULATE_BINLOG(thd) || mysql_bin_log.is_open()) &&
-      (!error || thd->transaction.stmt.modified_non_trans_table))
 #else
   if (mysql_bin_log.is_open() &&
-      (!error || thd->transaction.stmt.modified_non_trans_table))
 #endif
+      (!error || thd->transaction.stmt.modified_non_trans_table))
   {
     int errcode= 0;
     if (!error)
@@ -3715,7 +3714,7 @@ bool select_insert::send_eof()
                       trans_table, FALSE, FALSE, errcode))
     {
       table->file->ha_release_auto_increment();
-      DBUG_RETURN(1);
+      DBUG_RETURN(true);
     }
   }
   table->file->ha_release_auto_increment();
@@ -3723,27 +3722,49 @@ bool select_insert::send_eof()
   if (error)
   {
     table->file->print_error(error,MYF(0));
-    DBUG_RETURN(1);
+    DBUG_RETURN(true);
   }
-  char buff[160];
+
+  DBUG_RETURN(false);
+}
+
+bool select_insert::send_ok_packet() {
+  char  message[160];                           /* status message */
+  ulong row_count;                              /* rows affected */
+  ulong id;                                     /* last insert-id */
+
+  DBUG_ENTER("select_insert::send_ok_packet");
+
   if (info.ignore)
-    sprintf(buff, ER(ER_INSERT_INFO), (ulong) info.records,
-	    (ulong) (info.records - info.copied),
-            (ulong) thd->warning_info->statement_warn_count());
+    my_snprintf(message, sizeof(message), ER(ER_INSERT_INFO),
+                (ulong) info.records, (ulong) (info.records - info.copied),
+                (ulong) thd->warning_info->statement_warn_count());
   else
-    sprintf(buff, ER(ER_INSERT_INFO), (ulong) info.records,
-	    (ulong) (info.deleted+info.updated),
-            (ulong) thd->warning_info->statement_warn_count());
+    my_snprintf(message, sizeof(message), ER(ER_INSERT_INFO),
+                (ulong) info.records, (ulong) (info.deleted + info.updated),
+                (ulong) thd->warning_info->statement_warn_count());
+
   row_count= info.copied + info.deleted +
-             ((thd->client_capabilities & CLIENT_FOUND_ROWS) ?
-              info.touched : info.updated);
+    ((thd->client_capabilities & CLIENT_FOUND_ROWS) ?
+     info.touched : info.updated);
+
   id= (thd->first_successful_insert_id_in_cur_stmt > 0) ?
     thd->first_successful_insert_id_in_cur_stmt :
     (thd->arg_of_last_insert_id_function ?
      thd->first_successful_insert_id_in_prev_stmt :
      (info.copied ? autoinc_value_of_last_inserted_row : 0));
-  ::my_ok(thd, row_count, id, buff);
-  DBUG_RETURN(0);
+
+  ::my_ok(thd, row_count, id, message);
+
+  DBUG_RETURN(false);
+}
+
+bool select_insert::send_eof()
+{
+  bool res;
+  DBUG_ENTER("select_insert::send_eof");
+  res= (prepare_eof() || send_ok_packet());
+  DBUG_RETURN(res);
 }
 
 void select_insert::abort_result_set() {
@@ -4240,9 +4261,12 @@ void select_create::send_error(uint errcode,const char *err)
 
 bool select_create::send_eof()
 {
-  bool tmp=select_insert::send_eof();
-  if (tmp)
+  DBUG_ENTER("select_create::send_eof");
+  if (prepare_eof())
+  {
     abort_result_set();
+    DBUG_RETURN(true);
+  }
   else
   {
     /*
@@ -4262,7 +4286,7 @@ bool select_create::send_eof()
                     thd->thread_id, thd->wsrep_conflict_state, thd->query());
         mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
         abort_result_set();
-	return TRUE;
+        DBUG_RETURN(true);
       }
       mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
 #endif /* WITH_WSREP */
@@ -4270,6 +4294,9 @@ bool select_create::send_eof()
 
     table->file->extra(HA_EXTRA_NO_IGNORE_DUP_KEY);
     table->file->extra(HA_EXTRA_WRITE_CANNOT_REPLACE);
+
+    send_ok_packet();
+
     if (m_plock)
     {
       mysql_unlock_tables(thd, *m_plock);
@@ -4277,7 +4304,7 @@ bool select_create::send_eof()
       m_plock= NULL;
     }
   }
-  return tmp;
+  DBUG_RETURN(false);
 }
 
 

sql/wsrep_mysqld.cc

@@ -1476,10 +1476,21 @@ void wsrep_to_isolation_end(THD *thd)
       gra->wsrep_exec_mode, gra->wsrep_query_state, gra->wsrep_conflict_state, \
       gra->command, gra->lex->sql_command, gra->query());
 
+/**
+  Check if request for the metadata lock should be granted to the requester.
+
+  @param  requestor_ctx        The MDL context of the requestor
+  @param  ticket               MDL ticket for the requested lock
+
+  @retval TRUE   Lock request can be granted
+  @retval FALSE  Lock request cannot be granted
+*/
+
 bool
 wsrep_grant_mdl_exception(MDL_context *requestor_ctx,
                           MDL_ticket *ticket
 ) {
+  /* Fallback to the non-wsrep behaviour */
   if (!WSREP_ON) return FALSE;
 
   THD *request_thd  = requestor_ctx->get_thd();

sql/wsrep_thd.cc

@@ -495,6 +495,17 @@ int wsrep_abort_thd(void *bf_thd_ptr, void *victim_thd_ptr, my_bool signal)
            bf_thd->wsrep_exec_mode == TOTAL_ORDER) )               &&
        victim_thd)
   {
+    if ((victim_thd->wsrep_conflict_state == MUST_ABORT) ||
+        (victim_thd->wsrep_conflict_state == ABORTED) ||
+        (victim_thd->wsrep_conflict_state == ABORTING))
+    {
+      WSREP_DEBUG("wsrep_abort_thd called by %llu with victim %llu already "
+                  "aborted. Ignoring.",
+                  (bf_thd) ? (long long)bf_thd->real_id : 0,
+                  (long long)victim_thd->real_id);
+      DBUG_RETURN(1);
+    }
+
     WSREP_DEBUG("wsrep_abort_thd, by: %llu, victim: %llu", (bf_thd) ?
                 (long long)bf_thd->real_id : 0, (long long)victim_thd->real_id);
     ha_wsrep_abort_transaction(bf_thd, victim_thd, signal);