MySQL Bug #12408412: GROUP_CONCAT + ORDER BY + INPUT/OUTPUT SAME USER VARIABLE = CRASH
and
MySQL Bug#14664077 SEVERE PERFORMANCE DEGRADATION IN SOME CASES WHEN USER VARIABLES ARE USED
sql/item_func.cc:
don't use anything from Item_func_set_user_var::fix_fields()
in Item_func_set_user_var::save_item_result()
sql/sql_class.cc:
Call suv->save_item_result(item) *before* doing suv->fix_fields(), because
the former evaluates the item (and caches its value), while the latter marks
the user variable as non-const. The problem is that the item was fix_field'ed
when the user variable was const, and it doesn't expect it to change to non-const
in the middle of the execution.
mysys/errors.c:
revert upstream's fix. use a much simpler one
mysys/my_write.c:
revert upstream's fix. use a simpler one
sql/item_xmlfunc.cc:
useless, but ok
sql/mysqld.cc:
simplify upstream's fix
storage/heap/hp_delete.c:
remove upstream's fix.
we'll use a much less expensive approach.
Fix that CHANGE MASTER ... MASTER_GTID_POS="" works to start from the very
beginning of the binary log (with test case).
Fix that not finding the requested GTID position in master binlog results in
fatal error, not endless connect retry.
Add test case demonstrating multi-source replication with GTID.
Test that we can move from being slave of two masters to be a slave
deeper down in the hierarchy (of a higher-up multi-source slave),
and vice versa.
The function remove_eq_cond removes the parts of a disjunction
for which it has been proved that they are always true. In the
result of this removal the disjunction may be converted into a
formula without OR that must be merged into the the AND formula
that contains the disjunction.
The merging of two AND conditions must take into account the
multiple equalities that may be part of each of them.
These multiple equality must be merged and become part of the
and object built as the result of the merge of the AND conditions.
Erroneously the function remove_eq_cond lacked the code that
would merge multiple equalities of the merged AND conditions.
This could lead to confusing situations when at the same AND
level there were two multiple equalities with common members
and the list of equal items contained only some of these
multiple equalities.
This, in its turn, could lead to an incorrect work of the
function substitute_for_best_equal_field when it tried to optimize
ref accesses. This resulted in forming invalid TABLE_REF objects
that were used to build look-up keys when materialized subqueries
were exploited.
- Fix that binlog_gtid_pos() (and hence slave connect) does not work
correctly in the very first binlog file (due to not logging empty
Gtid_list_log_event).
- Remove one instance of the stupid domain_id-0-is-implicit.
- Rename the confusing Gtid_Pos_Auto in SHOW SLAVE STATUS to Using_Gtid.
- Fix memory leak.
- Fixing a bug that DBNAME value was forgotten when followed by OPTION_LIST.
modified:
mysql-test/suite/connect/r/mysql.result
mysql-test/suite/connect/t/mysql.test
storage/connect/ha_connect.cc
This bug in the legacy code could manifest itself in queries with
semi-join materialized subqueries.
When a subquery is materialized all conditions that are imposed
only on the columns belonging to the tables from the subquery
are taken into account.The code responsible for subquery optimizations
that employes subquery materialization makes sure to remove these
conditions from the WHERE conditions of the query obtained after
it has transformed the original query into a query with a semi-join.
If the condition to be removed is an equality condition it could
be added to ON expressions and/or conditions from disjunctive branches
(parts of OR conditions) in an attempt to generate better access keys
to the tables of the query. Such equalities are supposed to be removed
later from all the formulas where they have been added to.
However, erroneously, this was not done in some cases when an ON
expression and/or a disjunctive part of the OR condition could
be converted into one multiple equality. As a result some equality
predicates over columns belonging to the tables of the materialized
subquery remained in the ON condition and/or the a disjunctive
part of the OR condition, and the excuter later, when trying to
evaluate them, returned wrong answers as the values of the fields
from these equalities were not valid.
This happened because any standalone multiple equality (a multiple
equality that are not ANDed with any other predicates) lacked
the information about equality predicates inherited from upper
levels (in particular, inherited from the WHERE condition).
The fix adds a reference to such information to any standalone
multiple equality.
- Add first basic mysql-test-run test case which tests switch to new master
using MASTER_GTID_POS=AUTO.
- When we connect with GTID, do not use any old relay logs, as they may
contain the wrong events or be corrupt after crash.
- Fix old bug that fails replication if we receive a heartbeat event
immediately after an event was omitted in the stream from the master.
- Fix rpl_end to clear Gtid_Pos_Auto, to keep check_testcase happy.
The wrong result set returned by the left join query from
the bug test case happened due to several inconsistencies
and bugs of the legacy mysql code.
The bug test case uses an execution plan that employs a scan
of a materialized IN subquery from the WHERE condition.
When materializing such an IN- subquery the optimizer injects
additional equalities into the WHERE clause. These equalities
express the constraints imposed by the subquery predicate.
The injected equality of the query in the test case happens
to belong to the same equality class, and a new equality
imposing a condition on the rows of the materialized subquery
is inferred from this class. Simultaneously the multiple
equality is added to the ON expression of the LEFT JOIN
used in the main query.
The inferred equality of the form f1=f2 is taken into account
when optimizing the scan of the rows the temporary table
that is the result of the subquery materialization: only the
values of the field f1 are read from the table into the record
buffer. Meanwhile the inferred equality is removed from the
WHERE conditions altogether as a constraint on the fields
of the temporary table that has been used when filling this table.
This equality is supposed to be removed from the ON expression
when the multiple equalities of the ON expression are converted
into an optimal set of equality predicates. It supposed to be
removed from the ON expression as an equality inferred from only
equalities of the WHERE condition. Yet, it did not happened
due to the following bug in the code.
Erroneously the code tried to build multiple equality for ON
expression twice: the first time, when it called optimize_cond()
for the WHERE condition, the second time, when it called
this function for the HAVING condition. When executing
optimize_con() for the WHERE condition a reference
to the multiple equality of the WHERE condition is set
in the multiple equality of the ON expression. This reference
would allow later to convert multiple equalities of the
ON expression into equality predicates. However the
the second call of build_equal_items() for the ON expression
that happened when optimize_cond() was called for the
HAVING condition reset this reference to NULL.
This bug fix blocks calling build_equal_items() for ON
expressions for the second time. In general, it will be
beneficial for many queries as it removes from ON
expressions any equalities that are to be checked for the
WHERE condition.
The patch also fixes two bugs in the list manipulation
operations and a bug in the function
substitute_for_best_equal_field() that resulted
in passing wrong reference to the multiple equalities
of where conditions when processing multiple
equalities of ON expressions.
The code of substitute_for_best_equal_field() and
the code the helper function eliminate_item_equal()
were also streamlined and cleaned up.
Now the conversion of the multiple equalities into
an optimal set of equality predicates first produces
the sequence of the all equalities processing multiple
equalities one by one, and, only after this, it inserts
the equalities at the beginning of the other conditions.
The multiple changes in the output of EXPLAIN
EXTENDED are mainly the result of this streamlining,
but in some cases is the result of the removal of
unneeded equalities from ON expressions. In
some test cases this removal were reflected in the
output of EXPLAIN resulted in disappearance of
“Using where” in some rows of the execution plans.
"mysqld --connect" conflicts with "mysqld --connect-timeout".
(unfortunate design decision in how mysqld handles command line options).
modified:
mysql-test/mysql-test-run.pl
mysql-test/suite/connect/suite.opt
mysql-test/suite/heap/heap.result:
Added test case
mysql-test/suite/heap/heap.test:
Added test case
storage/heap/hp_delete.c:
Fixed that we don't change order of keys for the current key when we delete them from the hash table.
Fixed that 'current_hash_ptr' is correct after heap_delete_key().
Don't "reset current_hash_ptr" on delete; This will improve time a lot for delete of rows when not all rows matches the search criteria.
Analysis:
Range analysis detects that the subquery is expensive and doesn't
build a range access method. Later, the applicability test for loose
scan doesn't take that into account, and builds a loose scan method
without a range scan on the min/max column. As a result loose scan
fetches the first key in each group, rather than the first key that
satisfies the condition on the min/max column.
Solution:
Since there is no SEL_ARG tree to be used for the min/max column,
it is not possible to use loose scan if the min/max column is compared
with an expensive scalar subquery. Make the test for loose scan
applicability to be in sync with the range analysis code by testing if
the min/max argument is compared with an expensive predicate.
There is actually one extra byte for the 11th character, however it seems
to be meant for the '\0' terminating byte in the DBF specifications.
Also, the third party software (e.g. OpenOffice) do not correctly open
tables with column length=11.
modified:
mysql-test/suite/connect/r/dbf.result
mysql-test/suite/connect/t/dbf.test
storage/connect/ha_connect.cc
- The "spath" column does not get replaces with $MYSQLD_DATADIR,
because it does not include the drive letter part, e.g. C:\.
Removing excluding spath from the "SELECT ... FROM dir1" query
- Warnings return slightly different text on Linux and Windows.
Linux has extra "/./" part:
DATADIR/./test/t1vec1
"--replace_result $MYSQLD_DATADIR DATADIR/" does not help.
Using --replace_regex instead.
modified:
mysql-test/suite/connect/r/vec.result
mysql-test/suite/connect/t/vec.test
