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BUG#27516 - divide by zero crash during optimize table

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When a table status is requested by statement like SHOW TABLE
STATUS and there is another statement (e.g. DELETE) sets
number of records to 0 concurrently, we may get division by
zero error, which crashes a server.

This is fixed by using thread local variable x->records instead
of shared info->state->records when we check if it is zero and
divide by it.


myisam/mi_info.c:
  Information schema does not lock a table when it requests table
  state info. If another thread sets info->state->records to 0
  after we check if it is 0 and before we divide by it we may get
  division by zero error.
  
  Check and divide by local x->records variable instead of shared
  info->state->records.
This commit is contained in:
unknown 2007-04-13 12:38:27 +05:00
commit f4a5f3c6ff
3 changed files with 76 additions and 3 deletions
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6
myisam/mi_info.c
View file

@ -57,9 +57,9 @@ int mi_status(MI_INFO *info, register MI_ISAMINFO *x, uint flag)
x->keys = share->state.header.keys;
x->check_time = share->state.check_time;
x->mean_reclength = info->state->records ?
(ulong) ((info->state->data_file_length-info->state->empty)/
info->state->records) : (ulong) share->min_pack_length;
x->mean_reclength= x->records ?
(ulong) ((x->data_file_length - x->delete_length) / x->records) :
(ulong) share->min_pack_length;
}
if (flag & HA_STATUS_ERRKEY)
{

35
mysql-test/r/bdb_notembedded.result Normal file
View file

@ -0,0 +1,35 @@
set autocommit=1;
reset master;
create table bug16206 (a int);
insert into bug16206 values(1);
start transaction;
insert into bug16206 values(2);
commit;
show binlog events;
Log_name Pos Event_type Server_id End_log_pos Info
f n Format_desc 1 n Server ver: VERSION, Binlog ver: 4
f n Query 1 n use `test`; create table bug16206 (a int)
f n Query 1 n use `test`; insert into bug16206 values(1)
f n Query 1 n use `test`; insert into bug16206 values(2)
drop table bug16206;
reset master;
create table bug16206 (a int) engine= bdb;
insert into bug16206 values(0);
insert into bug16206 values(1);
start transaction;
insert into bug16206 values(2);
commit;
insert into bug16206 values(3);
show binlog events;
Log_name Pos Event_type Server_id End_log_pos Info
f n Format_desc 1 n Server ver: VERSION, Binlog ver: 4
f n Query 1 n use `test`; create table bug16206 (a int) engine= bdb
f n Query 1 n use `test`; insert into bug16206 values(0)
f n Query 1 n use `test`; insert into bug16206 values(1)
f n Query 1 n use `test`; BEGIN
f n Query 1 n use `test`; insert into bug16206 values(2)
f n Query 1 n use `test`; COMMIT
f n Query 1 n use `test`; insert into bug16206 values(3)
drop table bug16206;
set autocommit=0;
End of 5.0 tests

38
mysql-test/t/bdb_notembedded.test Normal file
View file

@ -0,0 +1,38 @@
-- source include/not_embedded.inc
-- source include/have_bdb.inc
#
# Bug #16206: Superfluous COMMIT event in binlog when updating BDB in autocommit mode
#
set autocommit=1;
let $VERSION=`select version()`;
reset master;
create table bug16206 (a int);
insert into bug16206 values(1);
start transaction;
insert into bug16206 values(2);
commit;
--replace_result $VERSION VERSION
--replace_column 1 f 2 n 5 n
show binlog events;
drop table bug16206;
reset master;
create table bug16206 (a int) engine= bdb;
insert into bug16206 values(0);
insert into bug16206 values(1);
start transaction;
insert into bug16206 values(2);
commit;
insert into bug16206 values(3);
--replace_result $VERSION VERSION
--replace_column 1 f 2 n 5 n
show binlog events;
drop table bug16206;
set autocommit=0;
--echo End of 5.0 tests