There was a race condition in the rollback of TRX_UNDO_UPD_DEL_REC.
Once row_undo_mod_clust() has rolled back the changes by the rolling-back
transaction, it attempts to purge the delete-marked record, if possible, in a
separate mini-transaction.
However, row_undo_mod_remove_clust_low() fails to check if the DB_TRX_ID of
the record that it found after repositioning the cursor, is still the same.
If it is not, it means that the record was purged and another record was
inserted in its place.
So, the rollback would have performed an incorrect purge, breaking the
locking rules and causing corruption.
The problem was found by creating a table that contains a unique
secondary index and a primary key, and two threads running REPLACE
with only one value for the unique column, so that the uniqueness
constraint would be violated all the time, leading to statement
rollback.
This bug exists in all InnoDB versions (I checked MySQL 3.23.53).
It has become easier to repeat in 5.5 and 5.6 thanks to scalability
improvements and a dedicated purge thread.
rb#3085 approved by Jimmy Yang
There was a race condition in the rollback of TRX_UNDO_UPD_DEL_REC.
Once row_undo_mod_clust() has rolled back the changes by the rolling-back
transaction, it attempts to purge the delete-marked record, if possible, in a
separate mini-transaction.
However, row_undo_mod_remove_clust_low() fails to check if the DB_TRX_ID of
the record that it found after repositioning the cursor, is still the same.
If it is not, it means that the record was purged and another record was
inserted in its place.
So, the rollback would have performed an incorrect purge, breaking the
locking rules and causing corruption.
The problem was found by creating a table that contains a unique
secondary index and a primary key, and two threads running REPLACE
with only one value for the unique column, so that the uniqueness
constraint would be violated all the time, leading to statement
rollback.
This bug exists in all InnoDB versions (I checked MySQL 3.23.53).
It has become easier to repeat in 5.5 and 5.6 thanks to scalability
improvements and a dedicated purge thread.
rb#3085 approved by Jimmy Yang
Since the mtr_t struct is marked as invalid in DEBUG_VALGRIND build
during mtr_commit, checking mtr->inside_ibuf will cause this warning.
Also since mtr->inside_ibuf cannot be set in mtr_commit (assert check)
and mtr->state is set to MTR_COMMITTED, the 'ut_ad(!ibuf_inside(&mtr))'
check is not needed if 'ut_ad(mtr.state == MTR_COMMITTED)' is also
checked.
Since the mtr_t struct is marked as invalid in DEBUG_VALGRIND build
during mtr_commit, checking mtr->inside_ibuf will cause this warning.
Also since mtr->inside_ibuf cannot be set in mtr_commit (assert check)
and mtr->state is set to MTR_COMMITTED, the 'ut_ad(!ibuf_inside(&mtr))'
check is not needed if 'ut_ad(mtr.state == MTR_COMMITTED)' is also
checked.
SHUTDOWN IS IN PROGRESS
PROBLEM
-------
In the background thread srv_master_thread() we have a
a one second delay loop which will continuously monitor
server activity .If the server is inactive (with out any
user activity) or in a shutdown state we do some background
activity like flushing the changes.In the current code
we are not checking if server is in shutdown state before
sleeping for one second.
FIX
---
If server is in shutdown state ,then dont go to one second
sleep.
SHUTDOWN IS IN PROGRESS
PROBLEM
-------
In the background thread srv_master_thread() we have a
a one second delay loop which will continuously monitor
server activity .If the server is inactive (with out any
user activity) or in a shutdown state we do some background
activity like flushing the changes.In the current code
we are not checking if server is in shutdown state before
sleeping for one second.
FIX
---
If server is in shutdown state ,then dont go to one second
sleep.
Problem:
When the user specified foreign key name contains "_ibfk_", InnoDB wrongly
tries to rename it.
Solution:
When a table is renamed, all its associated foreign keys will also be renamed,
only if the foreign key names are automatically generated. If the foreign key
names are given by the user, even if it has _ibfk_ in it, it must not be
renamed.
rb#2935 approved by Jimmy, Krunal and Satya
Problem:
When the user specified foreign key name contains "_ibfk_", InnoDB wrongly
tries to rename it.
Solution:
When a table is renamed, all its associated foreign keys will also be renamed,
only if the foreign key names are automatically generated. If the foreign key
names are given by the user, even if it has _ibfk_ in it, it must not be
renamed.
rb#2935 approved by Jimmy, Krunal and Satya
SERIALIZABLE
Problem:
The documentation claims that WITH CONSISTENT SNAPSHOT will work for both
REPEATABLE READ and SERIALIZABLE isolation levels. But it will work only
for REPEATABLE READ isolation level. Also, the clause WITH CONSISTENT
SNAPSHOT is silently ignored when it is not applicable to the given isolation
level.
Solution:
Generate a warning when the clause WITH CONSISTENT SNAPSHOT is ignored.
rb#2797 approved by Kevin.
Note: Support team wanted to push this to 5.5+.
SERIALIZABLE
Problem:
The documentation claims that WITH CONSISTENT SNAPSHOT will work for both
REPEATABLE READ and SERIALIZABLE isolation levels. But it will work only
for REPEATABLE READ isolation level. Also, the clause WITH CONSISTENT
SNAPSHOT is silently ignored when it is not applicable to the given isolation
level.
Solution:
Generate a warning when the clause WITH CONSISTENT SNAPSHOT is ignored.
rb#2797 approved by Kevin.
Note: Support team wanted to push this to 5.5+.
MULTI-FILE TABLESPACE
ANALYSIS
--------
When a tablespace has multiple data files, InnoDB fails to
open the tablespace. This is because for each ibd file,
the first page is checked.But the first page of all ibd file
need not be the first page of the tablespace. Only the first
page of the tablespace contains the tablespace header. When
we check the first page of an ibd file that is not the first
page of the tablespace, then the "tablespace flags" is not
really available.This was wrongly used to check if a page is
corrupt or not.
FIX
---
Use the tablespace flags only if the page number is 0
in a tablespace.
[Approved by Inaam rb#2836 ]
MULTI-FILE TABLESPACE
ANALYSIS
--------
When a tablespace has multiple data files, InnoDB fails to
open the tablespace. This is because for each ibd file,
the first page is checked.But the first page of all ibd file
need not be the first page of the tablespace. Only the first
page of the tablespace contains the tablespace header. When
we check the first page of an ibd file that is not the first
page of the tablespace, then the "tablespace flags" is not
really available.This was wrongly used to check if a page is
corrupt or not.
FIX
---
Use the tablespace flags only if the page number is 0
in a tablespace.
[Approved by Inaam rb#2836 ]
Analysis
--------
The pthread_mutex commit_threads_m was initiliazed but never
used.
Fix
---
Removing the commit_threads_m mutex from the code base.
[ Approved by Marko rb#2475]
Analysis
--------
The pthread_mutex commit_threads_m was initiliazed but never
used.
Fix
---
Removing the commit_threads_m mutex from the code base.
[ Approved by Marko rb#2475]
DDL AND I_S QUERIES
Skip partially created indexes (ones whose name starts with TEMP_INDEX_PREFIX)
from stats gathering.
Because InnoDB reports HA_INPLACE_ADD_INDEX_NO_WRITE to MySQL, the latter
allows parallel execution of ha_innobase::add_index() and ha_innobase::info().
Reviewed by: Inaam (rb:2613)
DDL AND I_S QUERIES
Skip partially created indexes (ones whose name starts with TEMP_INDEX_PREFIX)
from stats gathering.
Because InnoDB reports HA_INPLACE_ADD_INDEX_NO_WRITE to MySQL, the latter
allows parallel execution of ha_innobase::add_index() and ha_innobase::info().
Reviewed by: Inaam (rb:2613)
IF IT HAS A WRONG COUNT
If CHECK TABLE finds that a secondary index contains the wrong
number of entries, it used to report an error but not mark the
index as corrupt. The error means that the index should be rebuilt,
which can be done with ALTER TABLE DROP INDEX and ALTER TABLE ADD
INDEX. But just in case the DBA does not pay any attention to the
output of CHECK TABLE, the secondary index should be marked as
corrupted so that it is not used again.
Approved by Inaam in RB:2607
IF IT HAS A WRONG COUNT
If CHECK TABLE finds that a secondary index contains the wrong
number of entries, it used to report an error but not mark the
index as corrupt. The error means that the index should be rebuilt,
which can be done with ALTER TABLE DROP INDEX and ALTER TABLE ADD
INDEX. But just in case the DBA does not pay any attention to the
output of CHECK TABLE, the secondary index should be marked as
corrupted so that it is not used again.
Approved by Inaam in RB:2607
ON DELETION ORDER
Problem:
When a InnoDB index page is under-filled, we will merge it with either
the left sibling node or the right sibling node. But this checking is
incorrect. When the left sibling node is available, even if merging
is not possible with left sibling node, we do not check for the
possibility of merging with the right sibling node.
Solution:
If left sibling node is available, and merging with left sibling node
is not possible, then check if merge with right sibling node is
possible.
rb#2506 approved by jimmy & ima.
ON DELETION ORDER
Problem:
When a InnoDB index page is under-filled, we will merge it with either
the left sibling node or the right sibling node. But this checking is
incorrect. When the left sibling node is available, even if merging
is not possible with left sibling node, we do not check for the
possibility of merging with the right sibling node.
Solution:
If left sibling node is available, and merging with left sibling node
is not possible, then check if merge with right sibling node is
possible.
rb#2506 approved by jimmy & ima.
bzr merge lp:maria/5.5 -rtag:mariadb-5.5.31
Text conflict in cmake/cpack_rpm.cmake
Text conflict in debian/dist/Debian/control
Text conflict in debian/dist/Ubuntu/control
Text conflict in sql/CMakeLists.txt
Conflict adding file sql/db.opt. Moved existing file to sql/db.opt.moved.
Conflict adding file sql/db.opt.moved. Moved existing file to sql/db.opt.moved.moved.
Text conflict in sql/mysqld.cc
Text conflict in support-files/mysql.spec.sh
8 conflicts encountered.
i_s_innodb_buffer_page_get_info(): Do not read the buffer block frame
contents of read-fixed blocks, because it may be invalid or
uninitialized. When we are going to decompress or read a block, we
will put it into buf_pool->page_hash and buf_pool->LRU, read-fix the
block and release the mutexes for the duration of the reading or
decompression.
rb#2500 approved by Jimmy Yang
i_s_innodb_buffer_page_get_info(): Do not read the buffer block frame
contents of read-fixed blocks, because it may be invalid or
uninitialized. When we are going to decompress or read a block, we
will put it into buf_pool->page_hash and buf_pool->LRU, read-fix the
block and release the mutexes for the duration of the reading or
decompression.
rb#2500 approved by Jimmy Yang
ESCAPED WITH BACKSLASH
Problem:
When the CREATE TABLE statement used COMMENTS with escape sequences like
'foo\'s', InnoDB did not parse is correctly when trying to extract the
foreign key information. Because of this, the foreign keys specified
in the CREATE TABLE statement were not created.
Solution:
Make the InnoDB internal parser aware of escape sequences.
rb#2457 approved by Kevin.
ESCAPED WITH BACKSLASH
Problem:
When the CREATE TABLE statement used COMMENTS with escape sequences like
'foo\'s', InnoDB did not parse is correctly when trying to extract the
foreign key information. Because of this, the foreign keys specified
in the CREATE TABLE statement were not created.
Solution:
Make the InnoDB internal parser aware of escape sequences.
rb#2457 approved by Kevin.
