Ensure that one can drop a trigger with an orphan .TRN file

Before this fix, one would get a 'Trigger ... already exists' when trying
to create a trigger matching the original name and 'Trigger ... does not
exists" when trying to drop it.

Fixes a reported bug in MDEV-25180 Atomic ALTER TABLE

MDEV-25517 Atomic DDL: Assertion `query_arg' in THD::binlog_query
upon DROP TRIGGER

The bug was that the stmt_query variable was not populated
with the query in case of DROP TRIGGER of an orphan trigger
(.TRN file exists & table exists, but the trigger was not in
table->triggers).

mysql-test/main/trigger.result

@@ -2450,3 +2450,41 @@ DROP TABLE t1;
 #
 # End of 10.3 tests
 #
+#
+# Test dropping orphan .trn file
+#
+create table t1 (a int);
+create trigger t1_trg before insert on t1 for each row
+begin
+if isnull(new.a) then
+set new.a:= 1000;
+end if;
+end|
+insert into t1 values (null);
+select * from t1;
+a
+1000
+drop table t1;
+drop trigger t1_trg;
+Warnings:
+Error	1146	Table 'test.t1' doesn't exist
+Warning	4181	Dropped orphan trigger 't1_trg', originally created for table: 't1'
+create table t1 (a int);
+drop trigger t1_trg;
+Warnings:
+Warning	4181	Dropped orphan trigger 't1_trg', originally created for table: 't1'
+create trigger t1_trg_2 before insert on t1 for each row
+begin
+if isnull(new.a) then
+set new.a:= 1000;
+end if;
+end|
+drop trigger t1_trg;
+Warnings:
+Error	1360	Trigger does not exist
+Warning	4181	Dropped orphan trigger 't1_trg', originally created for table: 't1'
+drop trigger t1_trg_2;
+drop table t1;
+#
+# End of 10.6 tests
+#

mysql-test/main/trigger.test

@@ -2782,3 +2782,48 @@ DROP TABLE t1;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo #
+--echo # Test dropping orphan .trn file
+--echo #
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+
+create table t1 (a int);
+delimiter |;
+create trigger t1_trg before insert on t1 for each row
+begin
+  if isnull(new.a) then
+    set new.a:= 1000;
+  end if;
+end|
+delimiter ;|
+insert into t1 values (null);
+select * from t1;
+
+--copy_file $MYSQLD_DATADIR/test/t1_trg.TRN $MYSQLD_DATADIR/test/t1_trg.TMP
+drop table t1;
+--copy_file $MYSQLD_DATADIR/test/t1_trg.TMP $MYSQLD_DATADIR/test/t1_trg.TRN
+drop trigger t1_trg;
+create table t1 (a int);
+--copy_file $MYSQLD_DATADIR/test/t1_trg.TMP $MYSQLD_DATADIR/test/t1_trg.TRN
+drop trigger t1_trg;
+
+# Test creating an additonal trigger for t1, but with different names
+delimiter |;
+create trigger t1_trg_2 before insert on t1 for each row
+begin
+  if isnull(new.a) then
+    set new.a:= 1000;
+  end if;
+end|
+delimiter ;|
+--copy_file $MYSQLD_DATADIR/test/t1_trg.TMP $MYSQLD_DATADIR/test/t1_trg.TRN
+drop trigger t1_trg;
+drop trigger t1_trg_2;
+drop table t1;
+--remove_file $MYSQLD_DATADIR/test/t1_trg.TMP
+
+--echo #
+--echo # End of 10.6 tests
+--echo #

mysql-test/suite/binlog/r/binlog_trigger.result

@@ -22,3 +22,17 @@ master-bin.000001	#	Gtid	#	#	GTID #-#-#
 master-bin.000001	#	Query	#	#	use `test`; CREATE DEFINER=`root`@`localhost` TRIGGER tr3_bi BEFORE INSERT ON t1 FOR EACH ROW precedes tr4_bi INSERT INTO t2 (a) VALUES (NEW.a + 400)
 master-bin.000001	#	Gtid	#	#	GTID #-#-#
 master-bin.000001	#	Query	#	#	use `test`; DROP TABLE `t1` /* generated by server */
+#
+# MDEV-25517 Atomic DDL: Assertion `query_arg' in THD::binlog_query
+# upon DROP TRIGGER
+#
+CREATE TABLE t1 (a INT);
+CREATE TRIGGER trg AFTER INSERT ON t1 FOR EACH ROW SET @x = 1;
+connect  con1,localhost,root,,test;
+DROP TRIGGER trg;
+connection default;
+DROP TRIGGER trg;
+connection con1;
+disconnect con1;
+connection default;
+DROP TABLE t1;

mysql-test/suite/binlog/t/binlog_trigger.test

@@ -21,3 +21,31 @@ DROP TABLE t1;
 
 --let $binlog_file = LAST
 source include/show_binlog_events.inc;
+
+--echo #
+--echo # MDEV-25517 Atomic DDL: Assertion `query_arg' in THD::binlog_query
+--echo # upon DROP TRIGGER
+--echo #
+
+# This test case is 'random' by design.  For most cases the second DROP TRIGGER
+# will generate a warning "Dropped orphan trigger...", but if there is a timing
+# issue, we may get another error or warning later. This is ok as it enables
+# us to have more code paths tested over time.
+
+CREATE TABLE t1 (a INT);
+CREATE TRIGGER trg AFTER INSERT ON t1 FOR EACH ROW SET @x = 1;
+--disable_warnings
+--connect (con1,localhost,root,,test)
+--send
+  DROP TRIGGER trg;
+--connection default
+--error 0,ER_TRG_DOES_NOT_EXIST
+DROP TRIGGER trg;
+# Cleanup
+--connection con1
+--error 0,ER_TRG_DOES_NOT_EXIST
+--reap
+--disconnect con1
+--connection default
+--enable_warnings
+DROP TABLE t1;

sql/share/errmsg-utf8.txt

@@ -7988,3 +7988,5 @@ ER_JSON_TABLE_MULTIPLE_MATCHES
         eng "Can't store multiple matches of the path in the column '%s' of JSON_TABLE '%s'."
 ER_WITH_TIES_NEEDS_ORDER
         eng "FETCH ... WITH TIES requires ORDER BY clause to be present"
+ER_REMOVED_ORPHAN_TRIGGER
+        eng "Dropped orphan trigger '%-.64s', originally created for table: '%-.192s'"

sql/sql_trigger.cc

@@ -39,6 +39,12 @@
 
 /*************************************************************************/
 
+static bool add_table_for_trigger_internal(THD *thd,
+                                           const sp_name *trg_name,
+                                           bool if_exists,
+                                           TABLE_LIST **table,
+                                           char *trn_path_buff);
+
 /**
   Trigger_creation_ctx -- creation context of triggers.
 */
@@ -396,6 +402,7 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   */
   TABLE *table;
   bool result= TRUE;
+  bool add_if_exists_to_binlog= 0, action_executed= 0;
   String stmt_query;
   bool lock_upgrade_done= FALSE;
   bool backup_of_table_list_done= 0;;
@@ -403,6 +410,7 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   MDL_request mdl_request_for_trn;
   Query_tables_list backup;
   DDL_LOG_STATE ddl_log_state, ddl_log_state_tmp_file;
+  char trn_path_buff[FN_REFLEN];
   DBUG_ENTER("mysql_create_or_drop_trigger");
 
   /* Charset of the buffer for statement must be system one. */
@@ -489,7 +497,8 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
       goto end;
     }
 
-    if (add_table_for_trigger(thd, thd->lex->spname, if_exists, & tables))
+    if (add_table_for_trigger_internal(thd, thd->lex->spname, if_exists, &tables,
+                                       trn_path_buff))
       goto end;
 
     if (!tables)
@@ -505,7 +514,8 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
       */
       result= FALSE;
       /* Still, we need to log the query ... */
-      stmt_query.append(thd->query(), thd->query_length());
+      stmt_query.set(thd->query(), thd->query_length(), system_charset_info);
+      action_executed= 1;
       goto end;
     }
   }
@@ -562,7 +572,15 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     tables->table= open_n_lock_single_table(thd, tables,
                                             TL_READ_NO_INSERT, 0);
     if (! tables->table)
+    {
+      if (!create && thd->get_stmt_da()->sql_errno() == ER_NO_SUCH_TABLE)
+      {
+        /* TRN file exists but table does not. Drop the orphan trigger */
+        thd->clear_error();                     // Remove error from open
+        goto drop_orphan_trn;
+      }
       goto end;
+    }
     tables->table->use_all_columns();
   }
   table= tables->table;
@@ -588,11 +606,7 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   if (!table->triggers)
   {
     if (!create)
-    {
-      my_error(ER_TRG_DOES_NOT_EXIST, MYF(0));
-      goto end;
-    }
-
+      goto drop_orphan_trn;
     if (!(table->triggers= new (&table->mem_root) Table_triggers_list(table)))
       goto end;
   }
@@ -618,7 +632,13 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
                                           &thd->lex->spname->m_name,
                                           &stmt_query,
                                           &ddl_log_state);
+    if (result)
+    {
+      thd->clear_error();                     // Remove error from drop trigger
+      goto drop_orphan_trn;
+    }
   }
+  action_executed= 1;
 
   close_all_tables_for_name(thd, table->s, HA_EXTRA_NOT_USED, NULL);
 
@@ -637,13 +657,19 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   sp_cache_invalidate();
 
 end:
-  if (!result)
+  if (!result && action_executed)
   {
+    ulonglong save_option_bits= thd->variables.option_bits;
+
     debug_crash_here("ddl_log_drop_before_binlog");
+    if (add_if_exists_to_binlog)
+      thd->variables.option_bits|= OPTION_IF_EXISTS;
     thd->binlog_xid= thd->query_id;
     ddl_log_update_xid(&ddl_log_state, thd->binlog_xid);
-    result= write_bin_log(thd, TRUE, stmt_query.ptr(), stmt_query.length());
+    result= write_bin_log(thd, TRUE, stmt_query.ptr(),
+                          stmt_query.length());
     thd->binlog_xid= 0;
+    thd->variables.option_bits= save_option_bits;
     debug_crash_here("ddl_log_drop_after_binlog");
   }
   ddl_log_complete(&ddl_log_state);
@@ -679,6 +705,16 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
 wsrep_error_label:
   DBUG_RETURN(true);
 #endif
+
+drop_orphan_trn:
+  my_error(ER_REMOVED_ORPHAN_TRIGGER, MYF(ME_WARNING),
+           thd->lex->spname->m_name.str, tables->table_name.str);
+  mysql_file_delete(key_file_trg, trn_path_buff, MYF(0));
+  result= thd->is_error();
+  add_if_exists_to_binlog= 1;
+  action_executed= 1;                           // Ensure query is binlogged
+  stmt_query.set(thd->query(), thd->query_length(), system_charset_info);
+  goto end;
 }
 
 
@@ -1862,17 +1898,16 @@ void Trigger::get_trigger_info(LEX_CSTRING *trigger_stmt,
     @retval TRUE  Otherwise.
 */
 
-bool add_table_for_trigger(THD *thd,
-                           const sp_name *trg_name,
-                           bool if_exists,
-                           TABLE_LIST **table)
+static bool add_table_for_trigger_internal(THD *thd,
+                                           const sp_name *trg_name,
+                                           bool if_exists,
+                                           TABLE_LIST **table,
+                                           char *trn_path_buff)
 {
   LEX *lex= thd->lex;
-  char trn_path_buff[FN_REFLEN];
   LEX_CSTRING trn_path= { trn_path_buff, 0 };
   LEX_CSTRING tbl_name= null_clex_str;
-
-  DBUG_ENTER("add_table_for_trigger");
+  DBUG_ENTER("add_table_for_trigger_internal");
 
   build_trn_path(thd, trg_name, (LEX_STRING*) &trn_path);
 
@@ -1905,6 +1940,23 @@ bool add_table_for_trigger(THD *thd,
 }
 
 
+/*
+  Same as above, but with an allocated buffer.
+  This is called by mysql_excute_command() in is here to keep stack
+  space down in the caller.
+*/
+
+bool add_table_for_trigger(THD *thd,
+                           const sp_name *trg_name,
+                           bool if_exists,
+                           TABLE_LIST **table)
+{
+  char trn_path_buff[FN_REFLEN];
+  return add_table_for_trigger_internal(thd, trg_name, if_exists,
+                                        table, trn_path_buff);
+}
+
+
 /**
   Drop all triggers for table.