Commit 8995277a authored by unknown's avatar unknown
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A fix and a test case for Bug#19399 "res 'Lost Connection' when 

dropping/creating tables".

The bug could lead to a crash when multi-delete statements were
prepared and used with temporary tables.

The bug was caused by lack of clean-up of multi-delete tables before
re-execution of a prepared statement. In a statement like
DELETE t1 FROM t1, t2 WHERE ... the first table list (t1) is
moved to lex->auxilliary_table_list and excluded from lex->query_tables
or select_lex->tables. Thus it was unaccessible to reinit_stmt_before_use
and not cleaned up before re-execution of a prepared statement. 


mysql-test/r/ps.result:
  Updated test results (Bug#19399)
mysql-test/t/ps.test:
  A test case for Bug#19399 "Stored Procedures 'Lost Connection' when 
  dropping/creating tables": test that multi-delete
  tables are cleaned up properly before re-execution.
sql/sql_lex.cc:
  Always initialize auxilliary_table_list when we initialize the lex:
  this way we don't have to check that lex->sql_command equals to
  SQLCOM_DELETE_MULTI whenever we need to access auxilliary_table_list.
  In particular, in reinit_stmt_before_use we can simply check that
  auxilliary_table_list is not NULL and clean it up if the check returns
  a true value.
sql/sql_prepare.cc:
  Move the one table clean-up functionality to a method of st_table_list.
  Clean up auxiliary_table_list if it's not empty.
sql/table.cc:
  Implement st_table_list::reinit_before_use().
sql/table.h:
  Declare st_table_list::reinit_before_use().
parent d94521c3

mysql-test/r/ps.result

+14 −0
Original line number Diff line number Diff line
@@ -875,3 +875,17 @@ select @@max_prepared_stmt_count, @@prepared_stmt_count; 
@@max_prepared_stmt_count	@@prepared_stmt_count

3	0

set global max_prepared_stmt_count= @old_max_prepared_stmt_count;

drop table if exists t1;

create temporary table if not exists t1 (a1 int);

prepare stmt from "delete t1 from t1 where (cast(a1/3 as unsigned) * 3) = a1";

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

execute stmt;

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

execute stmt;

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

execute stmt;

drop temporary table t1;

deallocate prepare stmt;

mysql-test/t/ps.test

+25 −0
Original line number Diff line number Diff line
@@ -926,4 +926,29 @@ select @@max_prepared_stmt_count, @@prepared_stmt_count; 
set global max_prepared_stmt_count= @old_max_prepared_stmt_count;

--enable_ps_protocol



#

# Bug#19399 "Stored Procedures 'Lost Connection' when dropping/creating

#            tables"

# Check that multi-delete tables are also cleaned up before re-execution.

# 

--disable_warnings

drop table if exists t1;

create temporary table if not exists t1 (a1 int);

--enable_warnings

# exact delete syntax is essential

prepare stmt from "delete t1 from t1 where (cast(a1/3 as unsigned) * 3) = a1";

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

# the server crashed on  the next statement without the fix

execute stmt;

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

# the problem was in memory corruption: repeat the test just in case

execute stmt;

drop temporary table t1;

create temporary table if not exists t1 (a1 int);

execute stmt;

drop temporary table t1;

deallocate prepare stmt;



# End of 4.1 tests

sql/sql_lex.cc

+1 −0
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ void lex_start(THD *thd, uchar *buf,uint length) 
  lex->value_list.empty();

  lex->update_list.empty();

  lex->param_list.empty();

  lex->auxilliary_table_list.empty();

  lex->unit.next= lex->unit.master=

    lex->unit.link_next= lex->unit.return_to= 0;

  lex->unit.prev= lex->unit.link_prev= 0;

sql/sql_prepare.cc

+13 −7
Original line number Diff line number Diff line
@@ -1727,12 +1727,7 @@ static void reset_stmt_for_execute(Prepared_statement *stmt) 
	 tables;

	 tables= tables->next)

    {

      /*

        Reset old pointers to TABLEs: they are not valid since the tables

        were closed in the end of previous prepare or execute call.

      */

      tables->table= 0;

      tables->table_list= 0;

      tables->reinit_before_use(thd);

    }



    {
@@ -1743,6 +1738,17 @@ static void reset_stmt_for_execute(Prepared_statement *stmt) 
      unit->reinit_exec_mechanism();

    }

  }

  /*

    Cleanup of the special case of DELETE t1, t2 FROM t1, t2, t3 ...

    (multi-delete).  We do a full clean up, although at the moment all we

    need to clean in the tables of MULTI-DELETE list is 'table' member.

  */

  for (TABLE_LIST *tables= (TABLE_LIST*) lex->auxilliary_table_list.first;

       tables;

       tables= tables->next)

  {

    tables->reinit_before_use(thd);

  }

  lex->current_select= &lex->select_lex;

  if (lex->result)

    lex->result->cleanup();

sql/table.cc

+17 −0
Original line number Diff line number Diff line
@@ -1523,6 +1523,23 @@ db_type get_table_type(const char *name) 
  DBUG_RETURN(ha_checktype((enum db_type) (uint) *(head+3)));

}



/*

  Cleanup this table for re-execution.



  SYNOPSIS

    st_table_list::reinit_before_use()

*/



void st_table_list::reinit_before_use(THD * /* thd */)

{

  /*

    Reset old pointers to TABLEs: they are not valid since the tables

    were closed in the end of previous prepare or execute call.

  */

  table= 0;

  table_list= 0;

}





/*****************************************************************************

** Instansiate templates