Problem described in this bug report affects MyISAM tables only.
Running mysqld --flush instructs mysqld to sync all changes to disk
after each SQL statement. It worked well for INSERT and DELETE
statements, but it did sync for UPDATE only in case if there was
index change (change of colum that has an index). If no updated column
has an index, data wasn't synced to disk.
This fix makes UPDATE statement to sync data to disk even if there is
no index change (that is only data change) and mysqld is run with
--flush option.
Fixed a possible problem with reading of dynamic records
when a write cache is active. The cache must be flushed
whenever a part of the file in the write cache is to be
read.
Added a read optimization to _mi_read_dynamic_record().
No test case. This was a hypothetical but existing problem.
"temporary table with data directory option fails"
myisam should not use user-specified table name when creating
temporary tables and use generated connection specific real name.
Test included.
It was possible that fetching a record by an exact key value
(including the record pointer) could return a record with a
different key value. This happened only if a concurrent insert
added a record with the searched key value after the fetching
statement locked the table for read.
The search succeded on the key value, but the record was
rejected as it was past the file length that was remembered
at start of the fetching statement. With other words it was
rejected as being a concurrently inserted record.
The action to recover from this problem was to fetch the
record that is pointed at by the next key of the index.
This was repeated until a record below the file length was
found.
I do now avoid this loop if an exact match was searched.
If this match is beyond the file length, it is now treated
as "key not found". There cannot be another key with the
same record pointer.
A corrupt table with dynamic record format can crash the
server when trying to select from it.
I fixed the crash that resulted from the particular type
of corruption that has been reported for this bug.
No test case. To test it, one needs a table with a very special
corruption. The bug report contains a file with such a table.
CHECK TABLE could complain about a fully intact spatial index.
A wrong comparison operator was used for table checking.
The result was that it checked for non-matching spatial keys.
This succeeded if at least two different keys were present,
but failed if only the matching key was present.
I fixed the key comparison.
Very complex select statements can create temporary tables
that are too big to be represented as a MyISAM table.
This was not checked at table creation time, but only at
open time. The result was an attempt to delete the
"impossible" table.
But if the server is built --with-raid, MyISAM tries to
open the table before deleting the files. It needs to find
out if the table uses the raid support and how many raid
chunks there are. This is done with an open "for repair",
which will almost always succeed.
But in this case we have an "impossible" table. The open
failed. Hence the files were not deleted. Also the error
message was a bit unspecific.
I turned an open error in this situation into the assumption
of having no raid support on the table. Thus the normal data
file is tried to be deleted. This may however leave existing
raid chunks behind.
I also added a check in mi_create() to prevent the creation
of an "impossible" table. A more decriptive error message is
given in this case.
No test case. The required select statement is way too
large for the test suite. I added a test script to the
bug report.
CHECK TABLE did temporarily clear the auto_increment value.
It runs with a read lock, allowing other readers and
conurrent INSERTs. The latter could grab the wrong value
in this moment.
CHECK TABLE does no longer modify the auto_increment value.
Not even for a short moment.
Write operations on tables created in 4.x with index on variable
length column results in index crash. Even REPAIR TABLE wasn't able
to fix broken index.
Problem was that packed key length size wasn't restored correctly.
In 5.0 packed key length size is either 1 or 2. In 4.x this length
is always 2, but is saved as 0.
This fix ensures that key length size is restored correctly for 4.x
tables.
Updating data in HEAP table with BTREE index results in wrong index_length
counter value, which keeps growing after each update.
When inserting new record into tree counter is incremented by:
sizeof(TREE_ELEMENT) + key_size + tree->size_of_element
But when deleting element from tree it doesn't decrement counter by key_size:
sizeof(TREE_ELEMENT) + tree->size_of_element
This fix makes accurate allocated memory counter for tree. That is
decrease counter by key_size when deleting tree element.
Retrieving data from compressed MyISAM table which is bigger than 4G on 32-bit box
with mmap() support results in server crash.
mmap() accepts length of bytes to be mapped in second param, which is 32-bit
size_t. But we pass data_file_length, which is 64-bit my_off_t. As a result only
first data_file_length % 4G were mapped.
This fix adds additional condition for mmap() usage, that is use mmap() for
compressed table which size is no more than 4G on 32-bit platform.
Whenever 'myisamchk' needed to recreate a table,
the auto increment information was lost.
Now the forgotten element of the table creation
information is set correctly.
For "count(*) while index_column = value" an index read
is done. It consists of an index scan and retrieval of
each key.
For efficiency reasons the index scan stores the key in
the special buffer 'lastkey2' once only. At the first
iteration it notes this fact with the flag
HA_STATE_RNEXT_SAME in 'info->update'.
For efficiency reasons, the key retrieval for blobs
does not allocate a new buffer, but uses 'lastkey2'...
Now I clear the HA_STATE_RNEXT_SAME flag whenever the
buffer has been polluted. In this case, the index scan
copies the key value again (and sets the flag again).
Remove wrong fix for Bug#14397 - OPTIMIZE TABLE with an open HANDLER causes a crash
Safety fix for bug #13855 "select distinct with group by caused server crash"
