data and index files
It was possible if DATA/INDEX DIRECTORY is pointing to
symlinked MySQL data home directory.
Do not allow to drop data/index files implicitly symlinked
to data home directory. For such tables remove symlink only.
Repairing MyISAM table with fulltext indexes and low
myisam_sort_buffer_size may crash the server.
Estimation of number of index entries was done incorrectly,
causing further assertion failure or server crash.
Docs note: min value for myisam_sort_buffer_size has been
changed from 4 to 4096.
Invalid memory read if HANDLER ... READ NEXT is executed
after failed (e.g. empty table) HANDLER ... READ FIRST.
The problem was that we attempted to perform READ NEXT,
whereas there is no pivot available from failed READ FIRST.
With this fix READ NEXT after failed READ FIRST equals
to READ FIRST.
This bug affects MyISAM tables only.
When MyISAM writes newly created index page it may be
initialized partially. In other words some bytes of
sensible data and uninitialized tail of the page may
go into index file.
Under certain rare circumstances these hunks of memory
may contain data that would be otherwise inaccessible
to user, like passwords or data from other tables.
Fixed by initializing memory for temporary MyISAM key
buffer to '\0'.
No test case for this fix as it is heavily covered by
existing tests.
myisam tables
Queries following TRUNCATE of partitioned MyISAM table
may crash server if myisam_use_mmap is true.
Internally this is MyISAM bug, but limited to partitioned
tables, because MyISAM doesn't use ::delete_all_rows()
method for TRUNCATE, but goes via table recreate instead.
MyISAM didn't properly fall back to non-mmaped I/O after
mmap() failure. Was not repeatable on linux before, likely
because (quote from man mmap):
SUSv3 specifies that mmap() should fail if length is 0.
However, in kernels before 2.6.12, mmap() succeeded in
this case: no mapping was created and the call returned
addr. Since kernel 2.6.12, mmap() fails with the error
EINVAL for this case.
index cardinalities=1
Parallel repair didn't poroperly update index cardinality
in certain cases.
When myisam_sort_buffer_size is not enough to store all
keys, index cardinality was updated before index was
actually written, when no index statistic is available.
Spatial indexes were not checking for out-of-record condition in
the handler next command when the previous command didn't found
rows.
Fixed by making the rtree index to check for end of rows condition
before re-using the key from the previous search.
Fixed another crash if the tree has changed since the last search.
Added a test case for the other error.
insert...select
Queries following bulk insert into an empty MyISAM table
may break it. This was pure MyISAM problem.
When bulk insert into an empty table is complete, MyISAM
may want to enable indexes via repair by sort. If repair
by sort fails (e.g. insufficient buffer), MyISAM failover
to repair with key cache, requesting repair of data file.
Repair of data file performs data file substitution. This
means that current table instance will point to new data
file. Other cached table instances are still pointing to
an old, deleted data file.
This is fixed by not requesting repair of data file
during enable indexes.
Explicit REPAIR is not affected, since it flushes all
table instances.
Bulk REPLACE or bulk INSERT ... ON DUPLICATE KEY UPDATE may
break dynamic record MyISAM table.
The problem is limited to bulk REPLACE and INSERT ... ON
DUPLICATE KEY UPDATE, because only these operations may
be done via UPDATE internally and may request write cache.
When flushing write cache, MyISAM may write remaining
cached data at wrong position. Fixed by requesting write
cache to seek to a correct position.
Performing fulltext prefix search (a word with truncation
operator) may cause a dead-loop. ft_min_word_len value
doesn't matter actually.
The problem was introduced along with "smarter index merge"
optimization.
inside subquery
Re-setting a fulltext index was a no-operation if not all
the matches of a search were consumed by reading them.
This was preventing a joined table using a fulltext index
in a subquery that requires only 1 row of output (e.g. EXISTS)
from working correctly because the second execution of the
sub-query has the fulltext index cursor in a wrong state and
was not finding results.
Fixed by making the re-init code _ftb_init_index_search()
to re-set open cursors in addition to depleted ones.
BUG#47073 - valgrind errs, corruption,failed repair of partition,
low myisam_sort_buffer_size
Fixed race conditions discovered with the provided test case and
stabilized test case.
Implemented the server infrastructure for the fix:
1. Added a function LEX_STRING *thd_query_string(THD) to return
a LEX_STRING structure instead of char *.
This is the function that must be called in innodb instead of
thd_query()
2. Did some encapsulation in THD : aggregated thd_query and
thd_query_length into a LEX_STRING and made accessor and mutator
methods for easy code updating.
3. Updated the server code to use the new methods where applicable.
low myisam_sort_buffer_size
Repair by sort (default) or parallel repair of a MyISAM table
(doesn't matter partitioned or not) as well as bulk inserts
and enable indexes some times didn't failover to repair with
key cache.
The problem was that after unsuccessful attempt, data file was
closed. Whereas repair with key cache requires open data file.
Fixed by reopening data file.
Also fixed a valgrind warning, which may appear during repair
by sort or parallel repair with certain myisam_sort_buffer_size
number of rows and length of an index entry (very dependent).
Backport from 6.0 to 5.1.
Only those sync points are included, which are used in debug_sync.test.
The Debug Sync Facility allows to place synchronization points
in the code:
open_tables(...)
DEBUG_SYNC(thd, "after_open_tables");
lock_tables(...)
When activated, a sync point can
- Send a signal and/or
- Wait for a signal
Nomenclature:
- signal: A value of a global variable that persists
until overwritten by a new signal. The global
variable can also be seen as a "signal post"
or "flag mast". Then the signal is what is
attached to the "signal post" or "flag mast".
- send a signal: Assign the value (the signal) to the global
variable ("set a flag") and broadcast a
global condition to wake those waiting for
a signal.
- wait for a signal: Loop over waiting for the global condition until
the global value matches the wait-for signal.
Please find more information in the top comment in debug_sync.cc
or in the worklog entry.
INSERT ... SELECT ...
Problem was that when bulk insert is used on an empty
table/partition, it disables the indexes for better
performance, but in this specific case it also tries
to read from that partition using an index, which is
not possible since it has been disabled.
Solution was to allow index reads on disabled indexes
if there are no records.
Also reverted the patch for bug#38005, since that was a workaround
in the partitioning engine instead of a fix in myisam.
the auto_increment value
This is an alternative patch that instead of allowing RECREATE TABLE
on TRUNCATE TABLE it implements reset_auto_increment that is called
after delete_all_rows.
Note: this bug was fixed by Mattias Jonsson:
Pusing this patch: http://lists.mysql.com/commits/70370
This patch fixes compilation warning, "conversion from 'time_t' to 'ulong',
possible loss of data".
The fix is to typecast time_t to ulong before assigning it to ulong.
Backported this from 6.0-bugteam tree.
This patch adds corrections to the original patch
submitted 2009-04-08 (http://lists.mysql.com/commits/71607):
- fixed that the original patch didn't work because of an
incorrect condition;
- added a test case.
Killing the insert-select statement corrupts the MyISAM table only
when the destination table is empty and when it has indexes. When
we bulk insert huge data and if the destination table is empty we
disable the indexes for fast inserts, data is then inserted and
indexes are re-enabled after bulk_insert operation
Killing the query, aborts the repair table operation during enable
indexes phase leading to table corruption.
We now truncate the table when we detect that enable indexes is
killed for bulk insert query.As we have an empty table before the
operation, we can fix by truncating the table.
A bug in the initialization of key segment information made it point
to the wrong bit, since a bit index was used when its int value
was needed. This lead to misinterpretation of bit columns
read from MyISAM record format when a NULL bit pushed them over
a byte boundary.
Fixed by using the int value of the bit instead.
single quote fails in 5.1.x
Performing fulltext prefix search (a word with truncation
operator) may cause a dead-loop.
The problem was in smarter index merge algorithm - it was writing
record reference to an incorrect memory area.
Killing insert-select statement on MyISAM corrupts the table.
Killing the insert-select statement corrupts the MyISAM table only
when the destination table is empty and when it has indexes. When
we bulk insert huge data and if the destination table is empty we
disable the indexes for fast inserts, data is then inserted and
indexes are re-enabled after bulk_insert operation
Killing the query, aborts the repair table operation during enable
indexes phase leading to table corruption.
We now truncate the table when we detect that enable indexes is
killed for bulk insert query.As we have an empty table before the
operation, we can fix by truncating the table.
