BUG#12162 - one can start two transactions with the same XID.

Now we keep all active XID's in a hash

mysql-test/r/xa.result

@@ -22,6 +22,8 @@ a
 xa start 'testa','testb';
 insert t1 values (30);
 xa end 'testa','testb';
+xa start 'testa','testb';
+ERROR XAE08: XAER_DUPID: The XID already exists
 xa start 0x7465737462, 0x2030405060, 0xb;
 insert t1 values (40);
 xa end 'testb',' 0@P`',11;
@@ -35,11 +37,11 @@ formatID	gtrid_length	bqual_length	data
 11	5	5	testb 0@P`
 1	5	5	testatestb
 xa commit 'testb',0x2030405060,11;
+ERROR XAE04: XAER_NOTA: Unknown XID
 xa rollback 'testa','testb';
 xa start 'zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz';
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
 select * from t1;
 a
 20
-40
 drop table t1;

mysql-test/t/xa.test

@@ -31,6 +31,9 @@ xa end 'testa','testb';
 connect (con1,localhost,,,);
 connection con1;
 
+--error 1438
+xa start 'testa','testb';
+
 #        gtrid [ , bqual [ , formatID ] ]
 xa start 0x7465737462, 0x2030405060, 0xb;
 insert t1 values (40);
@@ -47,6 +50,7 @@ xa prepare 'testa','testb';
 
 xa recover;
 
+--error 1397
 xa commit 'testb',0x2030405060,11;
 xa rollback 'testa','testb';
 

sql/ha_innodb.cc

@@ -7037,7 +7037,7 @@ innobase_xa_prepare(
 		return(0);
 	}
 
-        trx->xid=thd->transaction.xid;
+        trx->xid=thd->transaction.xid_state.xid;
 
 	/* Release a possible FIFO ticket and search latch. Since we will
 	reserve the kernel mutex, we have to release the search system latch

sql/handler.cc

@@ -547,8 +547,8 @@ void trans_register_ha(THD *thd, bool all, handlerton *ht_arg)
   trans->ht[trans->nht++]=ht_arg;
   DBUG_ASSERT(*ht == ht_arg);
   trans->no_2pc|=(ht_arg->prepare==0);
-  if (thd->transaction.xid.is_null())
-    thd->transaction.xid.set(thd->query_id);
+  if (thd->transaction.xid_state.xid.is_null())
+    thd->transaction.xid_state.xid.set(thd->query_id);
   DBUG_VOID_RETURN;
 }
 
@@ -595,7 +595,7 @@ int ha_commit_trans(THD *thd, bool all)
   THD_TRANS *trans= all ? &thd->transaction.all : &thd->transaction.stmt;
   bool is_real_trans= all || thd->transaction.all.nht == 0;
   handlerton **ht= trans->ht;
-  my_xid xid= thd->transaction.xid.get_my_xid();
+  my_xid xid= thd->transaction.xid_state.xid.get_my_xid();
   DBUG_ENTER("ha_commit_trans");
 
   if (thd->in_sub_stmt)
@@ -695,7 +695,7 @@ int ha_commit_one_phase(THD *thd, bool all)
     trans->nht=0;
     trans->no_2pc=0;
     if (is_real_trans)
-      thd->transaction.xid.null();
+      thd->transaction.xid_state.xid.null();
     if (all)
     {
 #ifdef HAVE_QUERY_CACHE
@@ -751,7 +751,7 @@ int ha_rollback_trans(THD *thd, bool all)
     trans->nht=0;
     trans->no_2pc=0;
     if (is_real_trans)
-      thd->transaction.xid.null();
+      thd->transaction.xid_state.xid.null();
     if (all)
     {
       thd->variables.tx_isolation=thd->session_tx_isolation;
@@ -945,6 +945,7 @@ int ha_recover(HASH *commit_list)
           char buf[XIDDATASIZE*4+6]; // see xid_to_str
           sql_print_information("ignore xid %s", xid_to_str(buf, list+i));
 #endif
+          xid_cache_insert(list+i, XA_PREPARED);
           found_foreign_xids++;
           continue;
         }
@@ -1008,10 +1009,8 @@ bool mysql_xa_recover(THD *thd)
 {
   List<Item> field_list;
   Protocol *protocol= thd->protocol;
-  handlerton **ht= handlertons, **end_ht=ht+total_ha;
-  bool error=TRUE;
-  int len, got;
-  XID *list=0;
+  int i=0;
+  XID_STATE *xs;
   DBUG_ENTER("mysql_xa_recover");
 
   field_list.push_back(new Item_int("formatID",0,11));
@@ -1021,48 +1020,30 @@ bool mysql_xa_recover(THD *thd)
 
   if (protocol->send_fields(&field_list,
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
-    DBUG_RETURN(TRUE);
-
-  for (len= MAX_XID_LIST_SIZE ; list==0 && len > MIN_XID_LIST_SIZE; len/=2)
-  {
-    list=(XID *)my_malloc(len*sizeof(XID), MYF(0));
-  }
-  if (!list)
-  {
-    my_error(ER_OUTOFMEMORY, MYF(0), len);
     DBUG_RETURN(1);
-  }
 
-  for ( ; ht < end_ht ; ht++)
+  pthread_mutex_lock(&LOCK_xid_cache);
+  while (xs=(XID_STATE*)hash_element(&xid_cache, i++))
   {
-    if (!(*ht)->recover)
-      continue;
-    while ((got=(*(*ht)->recover)(list, len)) > 0 )
+    if (xs->xa_state==XA_PREPARED)
     {
-      XID *xid, *end;
-      for (xid=list, end=list+got; xid < end; xid++)
-      {
-        if (xid->get_my_xid())
-          continue; // skip "our" xids
       protocol->prepare_for_resend();
-        protocol->store_longlong((longlong)xid->formatID, FALSE);
-        protocol->store_longlong((longlong)xid->gtrid_length, FALSE);
-        protocol->store_longlong((longlong)xid->bqual_length, FALSE);
-        protocol->store(xid->data, xid->gtrid_length+xid->bqual_length,
+      protocol->store_longlong((longlong)xs->xid.formatID, FALSE);
+      protocol->store_longlong((longlong)xs->xid.gtrid_length, FALSE);
+      protocol->store_longlong((longlong)xs->xid.bqual_length, FALSE);
+      protocol->store(xs->xid.data, xs->xid.gtrid_length+xs->xid.bqual_length,
                       &my_charset_bin);
       if (protocol->write())
-          goto err;
+      {
+        pthread_mutex_unlock(&LOCK_xid_cache);
+        DBUG_RETURN(1);
       }
-      if (got < len)
-        break;
     }
   }
 
-  error=FALSE;
+  pthread_mutex_unlock(&LOCK_xid_cache);
   send_eof(thd);
-err:
-  my_free((gptr)list, MYF(0));
-  DBUG_RETURN(error);
+  DBUG_RETURN(0);
 }
 
 /*

sql/handler.h

@@ -227,11 +227,11 @@ struct xid_t {
   char data[XIDDATASIZE];  // not \0-terminated !
 
   bool eq(struct xid_t *xid)
-  { return !memcmp(this, xid, sizeof(long)*3+gtrid_length+bqual_length); }
+  { return !memcmp(this, xid, length()); }
   bool eq(long g, long b, const char *d)
   { return g == gtrid_length && b == bqual_length && !memcmp(d, data, g+b); }
   void set(struct xid_t *xid)
-  { memcpy(this, xid, sizeof(long)*3+xid->gtrid_length+xid->bqual_length); }
+  { memcpy(this, xid, xid->length()); }
   void set(long f, const char *g, long gl, const char *b, long bl)
   {
     formatID= f;
@@ -270,6 +270,11 @@ struct xid_t {
            !memcmp(data, MYSQL_XID_PREFIX, MYSQL_XID_PREFIX_LEN) ?
            quick_get_my_xid() : 0;
   }
+  uint length()
+  {
+    return sizeof(formatID)+sizeof(gtrid_length)+sizeof(bqual_length)+
+           gtrid_length+bqual_length;
+  }
 };
 typedef struct xid_t XID;
 

sql/mysqld.cc

@@ -1050,6 +1050,7 @@ void clean_up(bool print_message)
   (void) ha_panic(HA_PANIC_CLOSE);	/* close all tables and logs */
   if (tc_log)
     tc_log->close();
+  xid_cache_free();
   delete_elements(&key_caches, (void (*)(const char*, gptr)) free_key_cache);
   multi_keycache_free();
   end_thr_alarm(1);			/* Free allocated memory */
@@ -2920,6 +2921,11 @@ server.");
     using_update_log=1;
   }
 
+  if (xid_cache_init())
+  {
+    sql_print_error("Out of memory");
+    unireg_abort(1);
+  }
   if (ha_init())
   {
     sql_print_error("Can't init databases");

sql/share/errmsg.txt

@@ -5388,3 +5388,5 @@ ER_STACK_OVERRUN_NEED_MORE
 	eng "Thread stack overrun:  %ld bytes used of a %ld byte stack, and %ld bytes needed.  Use 'mysqld -O thread_stack=#' to specify a bigger stack."
 ER_TOO_LONG_BODY 42000 S1009
 	eng "Routine body for '%-.100s' is too long"
+ER_XAER_DUPID XAE08
+        eng "XAER_DUPID: The XID already exists"

sql/sql_base.cc

@@ -502,7 +502,7 @@ void close_thread_tables(THD *thd, bool lock_in_use, bool skip_derived,
   */
   bzero(&thd->transaction.stmt, sizeof(thd->transaction.stmt));
   if (!thd->active_transaction())
-    thd->transaction.xid.null();
+    thd->transaction.xid_state.xid.null();
 
   /* VOID(pthread_sigmask(SIG_SETMASK,&thd->block_signals,NULL)); */
   if (!lock_in_use)

sql/sql_class.cc

@@ -323,7 +323,8 @@ void THD::init_for_queries()
                       variables.trans_alloc_block_size,
                       variables.trans_prealloc_size);
 #endif
-  transaction.xid.null();
+  transaction.xid_state.xid.null();
+  transaction.xid_state.in_thd=1;
 }
 
 
@@ -358,9 +359,15 @@ void THD::cleanup(void)
 {
   DBUG_ENTER("THD::cleanup");
 #ifdef ENABLE_WHEN_BINLOG_WILL_BE_ABLE_TO_PREPARE
-  if (transaction.xa_state != XA_PREPARED)
+  if (transaction.xid_state.xa_state == XA_PREPARED)
+  {
+#error xid_state in the cache should be replaced by the allocated value
+  }
 #endif
+  {
     ha_rollback(this);
+    xid_cache_delete(&transaction.xid_state);
+  }
   if (locked_tables)
   {
     lock=locked_tables; locked_tables=0;
@@ -1841,3 +1848,81 @@ void THD::pop_open_tables_state()
   set_open_tables_state(state);
   DBUG_VOID_RETURN;
 }
+
+pthread_mutex_t LOCK_xid_cache;
+HASH xid_cache;
+
+static byte *xid_get_hash_key(const byte *ptr,uint *length,
+                                  my_bool not_used __attribute__((unused)))
+{
+  *length=((XID_STATE*)ptr)->xid.length();
+  return (byte *)&((XID_STATE*)ptr)->xid;
+}
+
+static void xid_free_hash (void *ptr)
+{
+  if (!((XID_STATE*)ptr)->in_thd)
+    my_free((byte *)ptr, MYF(0));
+}
+
+bool xid_cache_init()
+{
+  pthread_mutex_init(&LOCK_xid_cache, MY_MUTEX_INIT_FAST);
+  hash_init(&xid_cache, &my_charset_bin, 100, 0, 0,
+            xid_get_hash_key, xid_free_hash, 0) != 0;
+}
+
+void xid_cache_free()
+{
+  if (hash_inited(&xid_cache))
+  {
+    hash_free(&xid_cache);
+    pthread_mutex_destroy(&LOCK_xid_cache);
+  }
+}
+
+XID_STATE *xid_cache_search(XID *xid)
+{
+  pthread_mutex_lock(&LOCK_xid_cache);
+  XID_STATE *res=(XID_STATE *)hash_search(&xid_cache, (byte *)xid, xid->length());
+  pthread_mutex_unlock(&LOCK_xid_cache);
+  return res;
+}
+
+bool xid_cache_insert(XID *xid, enum xa_states xa_state)
+{
+  XID_STATE *xs;
+  my_bool res;
+  pthread_mutex_lock(&LOCK_xid_cache);
+  if (hash_search(&xid_cache, (byte *)xid, xid->length()))
+    res=0;
+  else if (!(xs=(XID_STATE *)my_malloc(sizeof(*xs), MYF(MY_WME))))
+    res=1;
+  else
+  {
+    xs->xa_state=xa_state;
+    xs->xid.set(xid);
+    xs->in_thd=0;
+    res=my_hash_insert(&xid_cache, (byte*)xs);
+  }
+  pthread_mutex_unlock(&LOCK_xid_cache);
+  return res;
+}
+
+bool xid_cache_insert(XID_STATE *xid_state)
+{
+  pthread_mutex_lock(&LOCK_xid_cache);
+  DBUG_ASSERT(hash_search(&xid_cache, (byte *)&xid_state->xid,
+                          xid_state->xid.length())==0);
+  my_bool res=my_hash_insert(&xid_cache, (byte*)xid_state);
+  pthread_mutex_unlock(&LOCK_xid_cache);
+  return res;
+}
+
+void xid_cache_delete(XID_STATE *xid_state)
+{
+  pthread_mutex_lock(&LOCK_xid_cache);
+  hash_delete(&xid_cache, (byte *)xid_state);
+  pthread_mutex_unlock(&LOCK_xid_cache);
+}
+

sql/sql_class.h

@@ -351,8 +351,6 @@ public:
   inline uint32 get_open_count() { return open_count; }
 };
 
-/* character conversion tables */
-
 
 typedef struct st_copy_info {
   ha_rows records;
@@ -631,7 +629,7 @@ typedef struct system_status_var
   ulong filesort_range_count;
   ulong filesort_rows;
   ulong filesort_scan_count;
-  /* Ppepared statements and binary protocol */
+  /* Prepared statements and binary protocol */
   ulong com_stmt_prepare;
   ulong com_stmt_execute;
   ulong com_stmt_send_long_data;
@@ -925,6 +923,22 @@ struct st_savepoint {
 enum xa_states {XA_NOTR=0, XA_ACTIVE, XA_IDLE, XA_PREPARED};
 extern const char *xa_state_names[];
 
+typedef struct st_xid_state {
+  /* For now, this is only used to catch duplicated external xids */
+  XID  xid;                           // transaction identifier
+  enum xa_states xa_state;            // used by external XA only
+  bool in_thd;
+} XID_STATE;
+
+extern pthread_mutex_t LOCK_xid_cache;
+extern HASH xid_cache;
+bool xid_cache_init(void);
+void xid_cache_free(void);
+XID_STATE *xid_cache_search(XID *xid);
+bool xid_cache_insert(XID *xid, enum xa_states xa_state);
+bool xid_cache_insert(XID_STATE *xid_state);
+void xid_cache_delete(XID_STATE *xid_state);
+
 /*
   A registry for item tree transformations performed during
   query optimization. We register only those changes which require
@@ -946,7 +960,7 @@ enum prelocked_mode_type {NON_PRELOCKED= 0, PRELOCKED= 1,
 
 
 /*
-  Class that holds information about tables which were open and locked
+  Class that holds information about tables which were opened and locked
   by the thread. It is also used to save/restore this information in
   push_open_tables_state()/pop_open_tables_state().
 */
@@ -1143,8 +1157,7 @@ public:
     THD_TRANS all;			// Trans since BEGIN WORK
     THD_TRANS stmt;			// Trans for current statement
     bool on;                            // see ha_enable_transaction()
-    XID  xid;                           // transaction identifier
-    enum xa_states xa_state;            // used by external XA only
+    XID_STATE xid_state;
     /*
        Tables changed in transaction (that must be invalidated in query cache).
        List contain only transactional tables, that not invalidated in query
@@ -1164,7 +1177,7 @@ public:
     st_transactions()
     {
       bzero((char*)this, sizeof(*this));
-      xid.null();
+      xid_state.xid.null();
       init_sql_alloc(&mem_root, ALLOC_ROOT_MIN_BLOCK_SIZE, 0);
     }
 #endif

sql/sql_parse.cc

@@ -2017,7 +2017,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   */
   bzero(&thd->transaction.stmt, sizeof(thd->transaction.stmt));
   if (!thd->active_transaction())
-    thd->transaction.xid.null();
+    thd->transaction.xid_state.xid.null();
 
   /* report error issued during command execution */
   if (thd->killed_errno() && !thd->net.report_error)
@@ -4502,14 +4502,15 @@ end_with_restore_list:
     break;
   }
   case SQLCOM_XA_START:
-    if (thd->transaction.xa_state == XA_IDLE && thd->lex->xa_opt == XA_RESUME)
+    if (thd->transaction.xid_state.xa_state == XA_IDLE &&
+        thd->lex->xa_opt == XA_RESUME)
     {
-      if (! thd->transaction.xid.eq(thd->lex->xid))
+      if (! thd->transaction.xid_state.xid.eq(thd->lex->xid))
       {
         my_error(ER_XAER_NOTA, MYF(0));
         break;
       }
-      thd->transaction.xa_state=XA_ACTIVE;
+      thd->transaction.xid_state.xa_state=XA_ACTIVE;
       send_ok(thd);
       break;
     }
@@ -4518,10 +4519,10 @@ end_with_restore_list:
       my_error(ER_XAER_INVAL, MYF(0));
       break;
     }
-    if (thd->transaction.xa_state != XA_NOTR)
+    if (thd->transaction.xid_state.xa_state != XA_NOTR)
     {
       my_error(ER_XAER_RMFAIL, MYF(0),
-               xa_state_names[thd->transaction.xa_state]);
+               xa_state_names[thd->transaction.xid_state.xa_state]);
       break;
     }
     if (thd->active_transaction() || thd->locked_tables)
@@ -4529,9 +4530,15 @@ end_with_restore_list:
       my_error(ER_XAER_OUTSIDE, MYF(0));
       break;
     }
-    DBUG_ASSERT(thd->transaction.xid.is_null());
-    thd->transaction.xa_state=XA_ACTIVE;
-    thd->transaction.xid.set(thd->lex->xid);
+    if (xid_cache_search(thd->lex->xid))
+    {
+      my_error(ER_XAER_DUPID, MYF(0));
+      break;
+    }
+    DBUG_ASSERT(thd->transaction.xid_state.xid.is_null());
+    thd->transaction.xid_state.xa_state=XA_ACTIVE;
+    thd->transaction.xid_state.xid.set(thd->lex->xid);
+    xid_cache_insert(&thd->transaction.xid_state);
     thd->options= ((thd->options & (ulong) ~(OPTION_STATUS_NO_TRANS_UPDATE)) |
                    OPTION_BEGIN);
     thd->server_status|= SERVER_STATUS_IN_TRANS;
@@ -4544,28 +4551,28 @@ end_with_restore_list:
       my_error(ER_XAER_INVAL, MYF(0));
       break;
     }
-    if (thd->transaction.xa_state != XA_ACTIVE)
+    if (thd->transaction.xid_state.xa_state != XA_ACTIVE)
     {
       my_error(ER_XAER_RMFAIL, MYF(0),
-               xa_state_names[thd->transaction.xa_state]);
+               xa_state_names[thd->transaction.xid_state.xa_state]);
       break;
     }
-    if (!thd->transaction.xid.eq(thd->lex->xid))
+    if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
     {
       my_error(ER_XAER_NOTA, MYF(0));
       break;
     }
-    thd->transaction.xa_state=XA_IDLE;
+    thd->transaction.xid_state.xa_state=XA_IDLE;
     send_ok(thd);
     break;
   case SQLCOM_XA_PREPARE:
-    if (thd->transaction.xa_state != XA_IDLE)
+    if (thd->transaction.xid_state.xa_state != XA_IDLE)
     {
       my_error(ER_XAER_RMFAIL, MYF(0),
-               xa_state_names[thd->transaction.xa_state]);
+               xa_state_names[thd->transaction.xid_state.xa_state]);
       break;
     }
-    if (!thd->transaction.xid.eq(thd->lex->xid))
+    if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
     {
       my_error(ER_XAER_NOTA, MYF(0));
       break;
@@ -4573,22 +4580,28 @@ end_with_restore_list:
     if (ha_prepare(thd))
     {
       my_error(ER_XA_RBROLLBACK, MYF(0));
-      thd->transaction.xa_state=XA_NOTR;
+      xid_cache_delete(&thd->transaction.xid_state);
+      thd->transaction.xid_state.xa_state=XA_NOTR;
       break;
     }
-    thd->transaction.xa_state=XA_PREPARED;
+    thd->transaction.xid_state.xa_state=XA_PREPARED;
     send_ok(thd);
     break;
   case SQLCOM_XA_COMMIT:
-    if (!thd->transaction.xid.eq(thd->lex->xid))
+    if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
     {
-      if (!(res= !ha_commit_or_rollback_by_xid(thd->lex->xid, 1)))
+      XID_STATE *xs=xid_cache_search(thd->lex->xid);
+      if (!xs || xs->in_thd)
         my_error(ER_XAER_NOTA, MYF(0));
       else
+      {
+        ha_commit_or_rollback_by_xid(thd->lex->xid, 1);
+        xid_cache_delete(xs);
         send_ok(thd);
+      }
       break;
     }
-    if (thd->transaction.xa_state == XA_IDLE &&
+    if (thd->transaction.xid_state.xa_state == XA_IDLE &&
         thd->lex->xa_opt == XA_ONE_PHASE)
     {
       int r;
@@ -4597,7 +4610,7 @@ end_with_restore_list:
       else
         send_ok(thd);
     }
-    else if (thd->transaction.xa_state == XA_PREPARED &&
+    else if (thd->transaction.xid_state.xa_state == XA_PREPARED &&
              thd->lex->xa_opt == XA_NONE)
     {
       if (wait_if_global_read_lock(thd, 0, 0))
@@ -4617,27 +4630,33 @@ end_with_restore_list:
     else
     {
       my_error(ER_XAER_RMFAIL, MYF(0),
-               xa_state_names[thd->transaction.xa_state]);
+               xa_state_names[thd->transaction.xid_state.xa_state]);
       break;
     }
     thd->options&= ~(ulong) (OPTION_BEGIN | OPTION_STATUS_NO_TRANS_UPDATE);
     thd->server_status&= ~SERVER_STATUS_IN_TRANS;
-    thd->transaction.xa_state=XA_NOTR;
+    xid_cache_delete(&thd->transaction.xid_state);
+    thd->transaction.xid_state.xa_state=XA_NOTR;
     break;
   case SQLCOM_XA_ROLLBACK:
-    if (!thd->transaction.xid.eq(thd->lex->xid))
+    if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
     {
-      if (!(res= !ha_commit_or_rollback_by_xid(thd->lex->xid, 0)))
+      XID_STATE *xs=xid_cache_search(thd->lex->xid);
+      if (!xs || xs->in_thd)
         my_error(ER_XAER_NOTA, MYF(0));
       else
+      {
+        ha_commit_or_rollback_by_xid(thd->lex->xid, 0);
+        xid_cache_delete(xs);
         send_ok(thd);
+      }
       break;
     }
-    if (thd->transaction.xa_state != XA_IDLE &&
-        thd->transaction.xa_state != XA_PREPARED)
+    if (thd->transaction.xid_state.xa_state != XA_IDLE &&
+        thd->transaction.xid_state.xa_state != XA_PREPARED)
     {
       my_error(ER_XAER_RMFAIL, MYF(0),
-               xa_state_names[thd->transaction.xa_state]);
+               xa_state_names[thd->transaction.xid_state.xa_state]);
       break;
     }
     if (ha_rollback(thd))
@@ -4646,7 +4665,8 @@ end_with_restore_list:
       send_ok(thd);
     thd->options&= ~(ulong) (OPTION_BEGIN | OPTION_STATUS_NO_TRANS_UPDATE);
     thd->server_status&= ~SERVER_STATUS_IN_TRANS;
-    thd->transaction.xa_state=XA_NOTR;
+    xid_cache_delete(&thd->transaction.xid_state);
+    thd->transaction.xid_state.xa_state=XA_NOTR;
     break;
   case SQLCOM_XA_RECOVER:
     res= mysql_xa_recover(thd);