It is triple bug with one test suite:
1. Incorrect outer table detection
2. Incorrect leaf table processing for multi-update (should be full like for usual updates and inserts)
3. ON condition fix_fields() fould be called for all tables of the query.
WHERE ONE OF SELECT* IS DISTINCT FAILS.
ISSUE:
------
There are 2 issues related to explain union.
1. If we have subquery with union of selects. And, one of
the select need temp table to materialize its results
then it will replace its query structure with a simple
select from temporary table. Trying to display new
internal temporary table scan resulted in crash. But to
display the query plan, we should save the original
query structure.
2. Multiple execution of prepared explain statement which
have union of subqueries resulted in crash. If we have
constant subqueries, fake select used in union operation
will be evaluated once before using it for explain.
During first execution we have set fake select options to
SELECT_DESCRIBE, but did not reset after the explain.
Hence during next execution of prepared statement during
first time evaluation of fake select we had our select
options as SELECT_DESCRIBE this resulted in improperly
initialized data structures and crash.
SOLUTION:
---------
1. If called by explain now we save the original query
structure. And this will be used for displaying.
2. Reset the fake select options after it is called for
explain of union.
sql/sql_select.cc:
Reset the fake select options after it is called for explain of union
sql/sql_union.cc:
If called by explain but not from select_describe and we
need a temp table, then we create a temp join to preserve
original query structure.
BREAKS RBR
Analysis:
--------
A table created using a query of the format:
CREATE TABLE t1 AS SELECT REPEAT('A',1000) DIV 1 AS a;
breaks the Row Based Replication.
The query above creates a table having a field of datatype
'bigint' with a display width of 3000 which is beyond the
maximum acceptable value of 255.
In the RBR mode, CREATE TABLE SELECT statement is
replicated as a combination of CREATE TABLE statement
equivalent to one the returned by SHOW CREATE TABLE and
row events for rows inserted. When this CREATE TABLE event
is executed on the slave, an error is reported:
Display width out of range for column 'a' (max = 255)
The following is the output of 'SHOW CREATE TABLE t1':
CREATE TABLE t1(`a` bigint(3000) DEFAULT NULL)
ENGINE=InnoDB DEFAULT CHARSET=latin1;
The problem is due to the combination of two facts:
1) The above CREATE TABLE SELECT statement uses the display
width of the result of DIV operation as the display width
of the column created without validating the width for out
of bound condition.
2) The DIV operation incorrectly returns the length of its first
argument as the display width of its result; thus allowing
creation of a table with an incorrect display width of 3000
for the field.
Fix:
----
This fix changes the DIV operation implementation to correctly
evaluate the display width of its result. We check if DIV's
results estimated width crosses maximum width for integer
value (21) and if yes set it to this maximum value.
This patch also fixes fixes maximum display width evaluation
for DIV function when its first argument is in UCS2.
The previous patch for this bug was unfortunately completely wrong.
The purpose of cached_charset is to remember which character set we
have installed currently in the THD, so that in the common case where
charset does not change between queries, we do not need to update it
in the THD. Thus, it is important that the cached_charset field is
tightly coupled to the THD for which it handles caching.
Thus the right place to put cached_charset seems to be in the THD.
This patch introduces a field THD:system_thread_info where such info
in general can be placed without further inflating the THD with unused
data for other threads (THD is already far too big as it is). It then
moves the cached_charset into this slot for the SQL driver thread and
for the parallel replication worker threads.
The THD::rpl_filter field is also moved inside system_thread_info, to
keep the size of THD unchanged. Moving further fields in to reduce the
size of THD is a separate task, filed as MDEV-6164.
Bug#18396916 MAIN.OUTFILE_LOADDATA TEST FAILS ON ARM, AARCH64, PPC/PPC64
The recorded results for the failing tests were wrong.
They were introduced by the patch for
Bug#30946 mysqldump silently ignores --default-character-set when used with --tab
Correct results were returned for platforms where 'char' is implemented as unsigned.
This was reported as
Bug#46895 Test "outfile_loaddata" fails (reproducible)
Bug#11755168 46895: TEST "OUTFILE_LOADDATA" FAILS (REPRODUCIBLE)
The patch for that bug fixed only parts of the problem,
leaving the incorrect results in the .result file.
Solution: use 'uchar' for field_terminator and line_terminator on all platforms.
Also: remove some un-necessary casts, leaving the ones we actually need.
Replication caches the character sets used in a query, to be able to quickly
reuse them for the next query in the common case of them not having changed.
In parallel replication, this caching needs to be per-worker-thread. The
code was not modified to handle this correctly, so the caching in one worker
could cause another worker to run a query using the wrong character set,
causing replication corruption.
I_S table
mdl_iterate() helper function (which is used by the plugin to iterate mdl
locks) acquired mutexes in reverse order.
Fixed by iterating MDL locks in two stages:
1. Iterate locks hash under the protection of hash mutex, store all
lock pointers in a thread local array and increment reference counter
for the lock.
2. Iterate local array without protection of hash mutex, handle destroyed
locks.
It somewhat echoes hack in MDL_map_partition::move_from_hash_to_lock_mutex.
MDEV-5980: EITS: if condition is used for REF access, its selectivity is still in filtered%
MDEV-5985: EITS: selectivity estimates look illogical for join and non-key equalities
MDEV-6003: EITS: ref access, keypart2=const vs keypart2=expr - inconsistent filtered% value
- Made a number of fixes in table_cond_selectivity() so that it returns
correct selectivity estimates.
- Added comments in related code.
Better comments
Back-ported from the mysql 5.6 code line the patch with
the following comment:
Fix for Bug#11757108 CHANGE IN EXECUTION PLAN FOR COUNT_DISTINCT_GROUP_ON_KEY
CAUSES PEFORMANCE REGRESSION
The cause for the performance regression is that the access strategy for the
GROUP BY query is changed form using "index scan" in mysql-5.1 to use "loose
index scan" in mysql-5.5. The index used for group by is unique and thus each
"loose scan" group will only contain one record. Since loose scan needs to
re-position on each "loose scan" group this query will do a re-position for
each index entry. Compared to just reading the next index entry as a normal
index scan does, the use of loose scan for this query becomes more expensive.
The cause for selecting to use loose scan for this query is that in the current
code when the size of the "loose scan" group is one, the formula for
calculating the cost estimates becomes almost identical to the cost of using
normal index scan. Differences in use of integer versus floating point arithmetic
can cause one or the other access strategy to be selected.
The main issue with the formula for estimating the cost of using loose scan is
that it does not take into account that it is more costly to do a re-position
for each "loose scan" group compared to just reading the next index entry.
Both index scan and loose scan estimates the cpu cost as:
"number of entries needed too read/scan" * ROW_EVALUATE_COST
The results from testing with the query in this bug indicates that the real
cost for doing re-position four to eight times higher than just reading the
next index entry. Thus, the cpu cost estimate for loose scan should be increased.
To account for the extra work to re-position in the index we increase the
cost for loose index scan to include the cost of navigating the index.
This is modelled as a function of the height of the b-tree:
navigation cost= ceil(log(records in table)/log(indexes per block))
* ROWID_COMPARE_COST;
This will avoid loose index scan being used for indexes where the "loose scan"
group contains very few index entries.
MDEV-5985: EITS: selectivity estimates look illogical for join and non-key equalities
MDEV-6003: EITS: ref access, keypart2=const vs keypart2=expr - inconsistent filtered% value
- Made a number of fixes in table_cond_selectivity() so that it returns
correct selectivity estimates.
- Added comments in related code.
back-ported the patch for bug #13256831 from mysql-5.6 code line.
Here's the comment this patch was provided with:
Fixed bug#13256831 - ERROR 1032 (HY000): CAN'T FIND RECORD.
This bug only occurs if a user tries to update a base table using
an updatable view and this view was created as a join for which
the clause 'WITH CHECK OPTION' was specified.
The reason for the bug was that when such an update was
executed, row positions were not properly handled for tables
that were not updated but had constraints that had to be
checked due to the 'WITH CHECK OPTION' clause.
The reason for the bug was that when such update is executed
then for tables specified in the view definition and
also listed in the 'WITH CHECK OPTION' clause the positioning to
row being updated is not performed.
Both bugs are caused by the same problem: the function optimize_cond() should
update the value of *cond_equal rather than the value of join->cond_equal,
because it is called not only for the WHERE condition, but for the HAVING
condition as well.
WRITTEN WHILE ROWS REMAINS
Problem:
========
When truncate table fails while using transactional based
engines even though the operation errors out we still
continue and log it to binlog. Because of this master has
data but the truncate will be written to binary log which
will cause inconsistency.
Analysis:
========
Truncate table can happen either through drop and create of
table or by deleting rows. In the second case the existing
code is written in such a way that even if an error occurs
the truncate statement will always be binlogged. Which is not
correct.
Binlogging of TRUNCATE TABLE statement should check whether
truncate is executed "transactionally or not". If the table
is transaction based we log the TRUNCATE TABLE only on
successful completion.
If table is non transactional there are possibilities that on
error we could have partial changes done hence in such cases
we do log in spite of errors as some of the lines might have
been removed, so the statement has to be sent to slave.
Fix:
===
Using table handler whether truncate table is being executed
in transaction based mode or not is identified and statement
is binlogged accordingly.
mysql-test/suite/binlog/r/binlog_truncate_kill.result:
Added test case to test the fix for Bug#17942050.
mysql-test/suite/binlog/t/binlog_truncate_kill.test:
Added test case to test the fix for Bug#17942050.
sql/sql_truncate.cc:
Check if truncation is successful or not and retun appropriate
return values so that binlogging can be done based on that.
sql/sql_truncate.h:
Added a new enum.
Add a testcase and backport this fix:
Bug#14338686: MYSQL IS GENERATING DIFFERENT AND SLOWER
(IN NEWER VERSIONS) EXECUTION PLAN
PROBLEM:
While checking for an index to sort for the order by clause
in this query
"SELECT datestamp FROM contractStatusHistory WHERE
contract_id = contracts.id ORDER BY datestamp asc limit 1;"
we do not calculate the number of rows to be examined correctly.
As a result we choose index 'idx_contractStatusHistory_datestamp'
defined on the 'datestamp' field, rather than choosing index
'contract_id'. And hence the lower performance.
ANALYSIS:
While checking if an index is present to give the records in
sorted order(datestamp), we consider the selectivity of the
'ref_key'(contract_id here) using 'table->quick_condition_rows'.
'ref_key' here can be an index from 'REF_ACCESS' or from 'RANGE'.
As this is a 'REF_ACCESS', 'table->quick_condition_rows' is not
set to the actual value which is 2. Instead is set to the number
of tuples present in the table indicating that every row that
is selected would be satisfying the condition present in the query.
Hence, the selectivity becomes 1 even when we choose the index
on the order by column instead of the join_condition.
But, in reality as only 2 rows satisy the condition, we need to
examine half of the entire data set to get one tuple when we
choose index on the order by column.
Had we chosen the 'REF_ACCESS' we would have examined only 2 tuples.
Hence the delay in executing the query specified.
FIX:
While calculating the selectivity of the ref_key:
For REF_ACCESS consider quick_rows[ref_key] if range
optimizer has an estimate for this key. Else consider
'rec_per_key' statistic.
For RANGE ACCESS consider 'table->quick_condition_rows'.
Revert the old patch revid:monty@askmonty.org-20100325133339-7mkel6valai0b4lb
This patch caused the InnoDB part of the transaction to not be marked
read-write in some cases, which messes up XA commit (and likely other
stuff as well).
The problem was in the validation of the input data for blob types.
When assigned binary data, the character blob types were only checking if
the length of these data is a multiple of the minimum char length for the
destination charset.
And since e.g. UTF-8's minimum character length is 1 (becuase it's
variable length) even byte sequences that are invalid utf-8 strings (e.g.
wrong leading byte etc) were copied verbatim into utf-8 columns when
coming from binary strings or fields.
Storing invalid data into string columns was having all kinds of ill effects
on code that assumed that the encoding data are valid to begin with.
Fixed by additionally checking the incoming binary string for validity when
assigning it to a non-binary string column.
Made sure the conversions to charsets with no known "invalid" ranges
are not covered by the extra check.
Removed trailing spaces.
Test case added.
- Make JOIN::const_key_parts include keyparts for which
the WHERE clause has an equality in form
"t.key_part=reference_outside_this_select"
- This allows to avoid filesort'ing in some cases (and also
avoid a difficult choice between using filesort or using an index)
The problem was that the view substitute its fields (on prepare) with reverting the change after execution. After prepare on optimization exists2in convertion substituted arguments of '=' with constsnt '1', but then one of the arguments of '=' was reverted to the view field reference.This lead to incorrect WHERE condition on the second execution.
To fix the problem we replace whole '=' with '1' permannently.
We need to use mysql_cond_broadcast() rather than _signal for
COND_thread_count, as there can be multiple waiters.
Thanks to Pavel Ivanov for reporting both the problem and the
solution.
MDEV-5984: EITS: Incorrect filtered% value for single-table select with range access
- Fix calculate_cond_selectivity_for_table() to work correctly with range accesses
over multi-component keys:
= First, take selectivity of all possible range scans into account. Remember which
fields were used bt the range scans.
= Then, calculate selectivity produced by sargable predicates on fields. If a
field was used in a possible range access, assume its selectivity is already
taken into account.
- Fix table_cond_selectivity(): when quick select is used, selectivity of
COND(table) is taken into account in matching_candidates_in_table(). In
table_cond_selectivity() we should not apply it for the second time.
(for case-insensitive filesystems)
sql/events.cc:
for "SHOW EVENTS IN db_name"
sql/sp_head.h:
for "CREATE EVENT", and everything SP-related
sql/sql_acl.cc:
privilege check for mysql_change_db()
sql/sql_db.cc:
for metadata locking of db names
sql/sql_parse.cc:
any_db is a constant, it is not writable
sql/sql_show.cc:
for SHOW CREATE TRIGGER and other trigger-related statements
MDEV-5971 Asymmetry between CAST(DATE'2001-00-00') to INT and TO CHAR in prepared statements
Consistently set maybe_null flag, even not-NULL temporal literal may become NULL
in the restrictive sql_mode.
