The problem is that since MyISAM's concurrent_insert is on by
default some concurrent SELECT statements might not see changes
made by INSERT statements in other connections, even if the
INSERT statement has returned.
The solution is to disable concurrent_insert so that INSERT
statements returns after the data is actually visible to other
statements.
100% effectively on Windows
The mysqltest docs state that the 'replace_result' command
doesn't perform any escape processing.
However the current implementation was processing backslash
escapes in the from/to strings.
This prevents replacing e.g. patch on windows (where backslash
is used as a path separator).
Fixed by removing the backslash escape processing from
'replace_result'.
for ENGINE=MRG_MYISAM (should be optimized out).
Before WL#3281 MERGE engine had the HA_NOT_EXACT_COUNT flag
unset, and it worked with COUNT optimization as desired.
After the removal of the HA_NOT_EXACT_COUNT flag neither
HA_STATS_RECORDS_IS_EXACT (opposite to former HA_NOT_EXACT_COUNT
flag) nor modern HA_HAS_RECORDS flag were not added to MERGE
table flag mask.
1. The HA_HAS_RECORDS table flag has been set.
2. The ha_myisammrg::records method has been overridden to
calculate total number of records in underlying tables.
When a zero length is provided to the my_decimal_length_to_precision
function along with unsigned_flag set to false it returns a negative value.
For queries that employs temporary tables may cause failed assertion or
excessive memory consumption while temporary table creation.
Now the my_decimal_length_to_precision and the my_decimal_precision_to_length
functions take unsigned_flag into account only if the length/precision
argument is non-zero.
The function test_if_skip_sort_order ignored any covering index used for ref
access of a table in a query with ORDER BY if this index was incompatible
with the ORDER BY list and there was another covering index compatible with
this list.
As a result sub-optimal execution plans were chosen for some queries with
ORDER BY clause.
impossible WHERE/HAVING clause
(subselect_single_select_engine::exec).
Allocation and initialization of joined table list t1, t2... of
subqueries like:
NOT IN (SELECT ... FROM t1,t2,... WHERE 0)
is optimized out, however server tries to traverse this list.
Grouping or ordering of long values in not indexed BLOB/TEXT columns
with GBK or BIG5 charsets crashes the server.
MySQL server uses sorting (the filesort procedure) in the temporary
table to evaluate the GROUP BY clause in case of lack of suitable index.
That procedure takes into account only first @max_sort_length bytes
(system variable, usually 1024) of TEXT/BLOB sorting key string.
The my_strnxfrm_gbk and my_strnxfrm_big5 fill temporary keys
with data of whole blob length instead of @max_sort_length bytes
length. That buffer overrun has been fixed.
when --master-data is used
When using the --master-data option with mysqldump, mysqldump uses
a FLUSH TABLES command. However, this statement got replicated to
the slave(s), which caused the slave(s) to block unnecessarily while
the FLUSH tables command completed.
Now, if the master-data option is set to one of the two "on" modes,
then use the "LOCAL" qualifier to ensure that it's not replicated.
