Bug#37536: Thread scheduling causes performance degradation at low thread count
Deprecated --skip-thread-priority startup option as newer versions of
the server won't change the thread priorities by default.
Giving threads different priorities might yield marginal improvements
in some platforms (where it actually works) but on the other hand it
might cause significant degradation depending on the thread count and
number of processors. Meddling with the thread priorities is a not a
safe bet as it is very dependent on the behavior of the cpu scheduler
and system where MySQL is being run.
From MySQL 6.0 and up the default behavior is that of not modifying
the threads priorities.
Server created "arc" directories inside database directories and
maintained there useless copies of .frm files.
Creation and renaming procedures of those copies as well as
creation of "arc" directories has been discontinued.
Removal procedure has been kept untouched to be able to
cleanup existent database directories by the DROP DATABASE
query. Also view renaming procedure has been updated to remove
these directories.
JOIN for the subselect wasn't cleaned if we came upon an error
during sub_select() execution. That leads to the assertion failure
in close_thread_tables()
part of the 6.0 code backported
per-file comments:
mysql-test/r/sp-error.result
Bug#37949 Crash if argument to SP is a subquery that returns more than one row
test result
mysql-test/t/sp-error.test
Bug#37949 Crash if argument to SP is a subquery that returns more than one row
test case
sql/sp_head.cc
Bug#37949 Crash if argument to SP is a subquery that returns more than one row
lex->unit.cleanup() call added if not substatement
The problem is that when statement-based replication was enabled,
statements such as INSERT INTO .. SELECT FROM .. and CREATE TABLE
.. SELECT FROM need to grab a read lock on the source table that
does not permit concurrent inserts, which would in turn be denied
if the source table is a log table because log tables can't be
locked exclusively.
The solution is to not take such a lock when the source table is
a log table as it is unsafe to replicate log tables under statement
based replication. Furthermore, the read lock that does not permits
concurrent inserts is now only taken if statement-based replication
is enabled and if the source table is not a log table.
In order to improve the performance when replicating to partitioned
myisam tables with row-based format, the number of rows of current
rows log event is estimated and used to setup storage engine for bulk
inserts.
A stored procedure involving substrings could crash the server on certain
platforms because of invalid memory reads.
During storing the new blob-field value, the cached value's address range
overlapped that of the new field value. This caused problems when the
cached value storage was reallocated to provide access for a new
characater set representation. The patch checks the address ranges, and if
they overlap, the new field value is copied to a new storage before it is
converted to the new character set.
and
Bug#33555: Group By Query does not correctly aggregate partitions
Backport of bug-33257 which is the same bug.
read_range_*() calls was not passed to the partition handlers,
but was translated to index_read/next family calls.
Resulting in duplicates rows and wrong aggregations.
The fix for bug 31887 was incomplete : it assumes that all the
field types returned by the IS_NUM macro are descendants of
Item_num and tries to zero-fill the values before doing constant
substitution with such fields when they are compared to constant string
values.
The only exception to this is Field_timestamp : it's in the IS_NUM
macro, but is not a descendant of Field_num.
Fixed by excluding timestamp fields (Field_timestamp) when zero-filling
when converting the constant to compare with to a string.
Note that this will not exclude the timestamp columns from const
propagation.
