Commit 5ad90356 authored by svoj@mysql.com/april.(none)'s avatar svoj@mysql.com/april.(none)
Browse files

BUG#21310 - Trees in SQL causing a "crashed" table with MyISAM storage engine 

An update that used a join of a table to itself and modified the
table on one side of the join reported the table as crashed or
updated wrong rows.

Fixed by creating temporary table for self-joined multi update statement.
parent d2fa9fd1

mysql-test/r/myisam.result

+16 −0
Original line number Diff line number Diff line
@@ -944,3 +944,19 @@ select * from t1; 
a

42

drop table t1;

CREATE TABLE t1(a VARCHAR(16));

INSERT INTO t1 VALUES('aaaaaaaa'),(NULL);

UPDATE t1 AS ta1, t1 AS ta2 SET ta1.a='aaaaaaaaaaaaaaaa';

SELECT * FROM t1;

a

aaaaaaaaaaaaaaaa

aaaaaaaaaaaaaaaa

DROP TABLE t1;

CREATE TABLE t1(a INT);

INSERT INTO t1 VALUES(1),(2);

UPDATE t1,t1 AS t2 SET t1.a=t1.a+2 WHERE t1.a=t2.a-1;

SELECT * FROM t1 ORDER BY a;

a

2

3

DROP TABLE t1;

mysql-test/t/myisam.test

+19 −0
Original line number Diff line number Diff line
@@ -890,4 +890,23 @@ connection default; 
select * from t1;

drop table t1;



#

# BUG#21310 - Trees in SQL causing a "crashed" table with MyISAM storage

#             engine

#



# A simplified test case that reflect crashed table issue.

CREATE TABLE t1(a VARCHAR(16));

INSERT INTO t1 VALUES('aaaaaaaa'),(NULL);

UPDATE t1 AS ta1, t1 AS ta2 SET ta1.a='aaaaaaaaaaaaaaaa';

SELECT * FROM t1;

DROP TABLE t1;



# A test case that reflect wrong result set.

CREATE TABLE t1(a INT);

INSERT INTO t1 VALUES(1),(2);

UPDATE t1,t1 AS t2 SET t1.a=t1.a+2 WHERE t1.a=t2.a-1;

SELECT * FROM t1 ORDER BY a;

DROP TABLE t1;



# End of 4.1 tests

sql/lock.cc

+1 −1
Original line number Diff line number Diff line
@@ -528,7 +528,7 @@ int mysql_lock_have_duplicate(THD *thd, TABLE *table, TABLE_LIST *tables) 
  for (; tables; tables= tables->next)

  {

    table2= tables->table;

    if (table2->tmp_table == TMP_TABLE)

    if (table2->tmp_table == TMP_TABLE || table == table2)

      continue;



    /* All tables in list must be in lock. */

sql/sql_update.cc

+59 −72
Original line number Diff line number Diff line
@@ -23,8 +23,6 @@ 
#include "mysql_priv.h"

#include "sql_select.h"



static bool safe_update_on_fly(JOIN_TAB *join_tab, List<Item> *fields);



/* Return 0 if row hasn't changed */



static bool compare_record(TABLE *table, ulong query_id)
@@ -846,27 +844,69 @@ int multi_update::prepare(List<Item> &not_used_values, 
  for (i=0 ; i < table_count ; i++)

    set_if_bigger(max_fields, fields_for_table[i]->elements);

  copy_field= new Copy_field[max_fields];

  DBUG_RETURN(thd->is_fatal_error != 0);

}





/*

    Mark all copies of tables that are updates to ensure that

    init_read_record() will not try to enable a cache on them

  Check if table is safe to update on fly



    The problem is that for queries like

  SYNOPSIS

    safe_update_on_fly()

    thd                 Thread handler

    join_tab            How table is used in join

    all_tables          List of tables

    fields              Fields that are updated



  NOTES

    We can update the first table in join on the fly if we know that

    a row in this table will never be read twice. This is true under

    the following conditions:



    UPDATE t1, t1 AS t2 SET t1.b=t2.c WHERE t1.a=t2.a;

    - We are doing a table scan and the data is in a separate file (MyISAM) or

      if we don't update a clustered key.



    the row buffer may contain things that doesn't match what is on disk

    which will cause an error when reading a row.

    (This issue is mostly relevent for MyISAM tables)

    - We are doing a range scan and we don't update the scan key or

      the primary key for a clustered table handler.



    - Table is not joined to itself.



  WARNING

    This code is a bit dependent of how make_join_readinfo() works.



  RETURN

    0		Not safe to update

    1		Safe to update

*/

  for (table_ref= all_tables;  table_ref; table_ref=table_ref->next)



static bool safe_update_on_fly(THD *thd, JOIN_TAB *join_tab,

                               TABLE_LIST *all_tables, List<Item> *fields)

{

    TABLE *table=table_ref->table;

    if ((tables_to_update & table->map) && 

	mysql_lock_have_duplicate(thd, table, update_tables))

      table->no_cache= 1;			// Disable row cache

  TABLE *table= join_tab->table;

  /* First check if a table is not joined to itself. */

  if (mysql_lock_have_duplicate(thd, table, all_tables))

    return 0;

  switch (join_tab->type) {

  case JT_SYSTEM:

  case JT_CONST:

  case JT_EQ_REF:

    return 1;					// At most one matching row

  case JT_REF:

    return !check_if_key_used(table, join_tab->ref.key, *fields);

  case JT_ALL:

    /* If range search on index */

    if (join_tab->quick)

      return !check_if_key_used(table, join_tab->quick->index,

				*fields);

    /* If scanning in clustered key */

    if ((table->file->table_flags() & HA_PRIMARY_KEY_IN_READ_INDEX) &&

	table->primary_key < MAX_KEY)

      return !check_if_key_used(table, table->primary_key, *fields);

    return 1;

  default:

    break;					// Avoid compler warning

  }

  DBUG_RETURN(thd->is_fatal_error != 0);

  return 0;

}
@@ -905,7 +945,7 @@ multi_update::initialize_tables(JOIN *join) 
      table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);

    if (table == main_table)			// First table in join

    {

      if (safe_update_on_fly(join->join_tab, &temp_fields))

      if (safe_update_on_fly(thd, join->join_tab, all_tables, &temp_fields))

      {

	table_to_update= main_table;		// Update table on the fly

	continue;
@@ -951,59 +991,6 @@ multi_update::initialize_tables(JOIN *join) 
  DBUG_RETURN(0);

}



/*

  Check if table is safe to update on fly



  SYNOPSIS

    safe_update_on_fly

    join_tab		How table is used in join

    fields		Fields that are updated



  NOTES

    We can update the first table in join on the fly if we know that

    a row in this tabel will never be read twice. This is true under

    the folloing conditions:



    - We are doing a table scan and the data is in a separate file (MyISAM) or

      if we don't update a clustered key.



    - We are doing a range scan and we don't update the scan key or

      the primary key for a clustered table handler.



  WARNING

    This code is a bit dependent of how make_join_readinfo() works.



  RETURN

    0		Not safe to update

    1		Safe to update

*/



static bool safe_update_on_fly(JOIN_TAB *join_tab, List<Item> *fields)

{

  TABLE *table= join_tab->table;

  switch (join_tab->type) {

  case JT_SYSTEM:

  case JT_CONST:

  case JT_EQ_REF:

    return 1;					// At most one matching row

  case JT_REF:

    return !check_if_key_used(table, join_tab->ref.key, *fields);

  case JT_ALL:

    /* If range search on index */

    if (join_tab->quick)

      return !check_if_key_used(table, join_tab->quick->index,

				*fields);

    /* If scanning in clustered key */

    if ((table->file->table_flags() & HA_PRIMARY_KEY_IN_READ_INDEX) &&

	table->primary_key < MAX_KEY)

      return !check_if_key_used(table, table->primary_key, *fields);

    return 1;

  default:

    break;					// Avoid compler warning

  }

  return 0;

}





multi_update::~multi_update()

{