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              UNIQUE::~UNIQUE | SQL/UNIQUES.CC:355

Analysis
========

Enabling the sort_buffer_size with a large value
can cause operations utilizing the sort buffer
like DELETE as mentioned in the bug report to
fail. 5.5 and 5.6 versions reports OOM error
while in 5.7+, the server crashes.

While initializing the mem_root for the sort buffer
tree, the block size for the mem_root is determined
from the 'sort_buffer_size' value. This unsigned
long value is typecasted to unsigned int, hence
it becomes zero. Further block_size computation
while initializing the mem_root results in a very
large block_size value. Hence while trying to
allocate a block during the DELETE operation,
an OOM error is reported. In case of 5.7+, the PFS
instrumentation for memory allocation, overshoots
the unsigned value and allocates a block of just
one byte. While trying to free the block of the
mem_root, the original block_size is used. This
triggers the crash since the server tries to free
unallocated memory.

Fix:
====
In order to restrict usage of such unreasonable
sort_buffer_size, the typecast of block size
to 'unsigned int' is removed and hence reports
OOM error across all versions for sizes
exceeding unsigned int range.

FULL
Bug#21753696: MAKE SHOW SLAVE STATUS NON BLOCKING IF IO
THREAD WAITS FOR DISK SPACE

Fixing a post push test issue.

               INTERVALS

ISSUE:
------
Some string functions return one or a combination of the
parameters as their result. Here the resultant string's
charset could be incorrectly set to that of the chosen
parameter.

This results in incorrect behavior when an ascii string is
expected.

SOLUTION:
---------
Since an ascii string is expected, val_str_ascii should
explicitly convert the string.

Part of the fix is a backport of Bug#22340858 for mysql-5.5
and mysql-5.6.

               IS NOT FOUND

DESCRIPTION
===========
If script mysqld_multi and utility my_print_defaults are in
the same folder (not included in $PATH) and the former is
made to run, it complaints that the mysqld binary is absent
eventhough the binary exists.

ANALYSIS
========
We've a subroutine my_which() mimicking the behaviour of
POSIX "which" command. Its current behaviour is to check
for a given argument as follows:
- Step 1: Assume the argument to be a command having full
fledged absolute path. If it exists "as-is", return the
argument (which will be pathname), else proceed to Step 2.
- Step 2: Assume the argument to be a plain command with no
aboslute path. Try locating it in all of the paths
(mentioned in $PATH) one by one. If found return the
pathname. If found nowhere, return NULL.

Currently when my_which(my_print_defaults) is called, it
returns from Step 1 (since utlity exists in current
folder) and doesn't proceed to Step 2. This is wrong since
the returned value is same as the argument i.e.
'my_print_default' which defies the purpose of this
subroutine whose job is to return a pathname either in Step
1 or Step 2.

Later when the utility is executed in subroutine
defaults_for_group(), it evaluates to NULL and returns the
same. This is because the plain command 'my_print_defaults
{options} ...' would execute properly only if
my_print_defaults exists in one of the paths (in $PATH). In
such a case, in the course of the flow it looks onto the
variable $mysqld_found which comes out to be NULL and
hence ethe error.

In this case, call to my_which should fail resulting in
script being aborted and thus avoiding this mess.

FIX
===
This utility my_print_defaults should be tested only in
Step 2 since it does not have an absolute path. Thus added
a condition in Step 1 so that is gets executed iff not
called for my_print_defaults thus bypassing it to proceed
to Step 2 where the check is made for various paths (in
$PATH)

FULL
Bug#21753696: MAKE SHOW SLAVE STATUS NON BLOCKING IF IO
THREAD WAITS FOR DISK SPACE

Problem:
========
Currently SHOW SLAVE STATUS blocks if IO thread waits for
disk space. This makes automation tools verifying
server health block on taking relevant action. Finally this
will create SHOW SLAVE STATUS piles.

Analysis:
=========
SHOW SLAVE STATUS hangs on mi->data_lock if relay log write
is waiting for free disk space while holding mi->data_lock.
mi->data_lock is needed to protect the format description
event (mi->format_description_event) which is accessed by
the clients running FLUSH LOGS and slave IO thread. Note
relay log writes don't need to be protected by
mi->data_lock, LOCK_log is used to protect relay log between
IO and SQL thread (see MYSQL_BIN_LOG::append_event). The
code takes mi->data_lock to protect
mi->format_description_event during relay log rotate which
might get triggered right after relay log write.

Fix:
====
Release the data_lock just for the duration of writing into
relay log.

Made change to ensure the following lock order is maintained
to avoid deadlocks.

data_lock, LOCK_log

data_lock is held during relay log rotations to protect
the description event.

REPLICATION

Problem: In RBR mode, merge table updates are not successfully applied on a cascading
replication.

Analysis & Fix: Every type of row event is preceded by one or more table_map_log_events
that gives the information about all the tables that are involved in the row
event. Server maintains the list in RPL_TABLE_LIST and it goes through all the
tables and checks for the compatibility between master and slave. Before
checking for the compatibility, it calls 'open_tables()' which takes the list
of all tables that needs to be locked and opened. In RBR, because of the
Table_map_log_event , we already have all the tables including base tables in
the list. But the open_tables() which is generic call takes care of appending
base tables if the list contains merge tables. There is an assumption in the
current replication layer logic that these tables (TABLE_LIST type objects) are always
added in the end of the list. Replication layer maintains the count of
tables(tables_to_lock_count) that needs to be verified for compatibility check
and runs through only those many tables from the list and rest of the objects
in linked list can be skipped. But this assumption is wrong.
open_tables()->..->add_children_to_list() adds base tables to the list immediately
after seeing the merge table in the list.

For eg: If the list passed to open_tables() is t1->t2->t3 where t3 is merge
table (and t1 and t2 are base tables), it adds t1'->t2' to the list after t3.
New table list looks like t1->t2->t3->t1'->t2'. It looks like it added at the
end of the list but that is not correct. If the list passed to open_tables()
is t3->t1->t2 where t3 is merge table (and t1 and t2 are base tables), the new
prepared list will be t3->t1'->t2'->t1->t2. Where t1' and t2' are of
TABLE_LIST objects which were added by add_children_to_list() call and replication
layer should not look into them. Here tables_to_lock_count  will not help as the
objects are added in between the list.

Fix: After investigating add_children_list() logic (which is called from open_tables()),
there is no flag/logic in it to skip adding the children to the list even if the
children are already included in the table list. Hence to fix the issue, a
logic should be added in the replication layer to skip children in the list by
checking whether  'parent_l' is non-null or not. If it is children, we will skip 'compatibility'
check for that table.

Also this patch is not removing 'tables_to_lock_count' logic for the performance issues
if there are any children at the end of the list, those can be easily skipped directly by
stopping the loop with tables_to_lock_count check.

              FOUND

Description:- Failure during the validation of CA
certificate path which is provided as an option for 'ssl-ca'
returns two different errors for YaSSL and OPENSSL.

Analysis:- 'ssl-ca', option used for specifying the ssl ca
certificate path. Failing to validate this certificate with
OPENSSL returns an error, "ERROR 2026 (HY000): SSL
connection error: SSL_CTX_set_default_verify_paths failed".
While YASSL returns "ERROR 2026 (HY000): SSL connection
error: ASN: bad other signature confirmation". Error
returned by the OPENSSL is correct since
"SSL_CTX_load_verify_locations()" returns 0 (in case of
OPENSSL) for the failure and sets error as
"SSL_INITERR_BAD_PATHS". In case of YASSL,
"SSL_CTX_load_verify_locations()" returns an error number
which is less than or equal to 0 in case of error. Error
numbers for YASSL is mentioned in the file,
'extra/yassl/include/openssl/ssl.h'(line no : 292). Also
'ssl-ca' does not accept tilde home directory path
substitution.

Fix:- The condition which checks for the error in the
"SSL_CTX_load_verify_locations()" is changed in order to
accommodate YASSL as well. A logic is written in
"mysql_ssl_set()" in order accept the tilde home directory
path substitution for all ssl options.

The main.merge test case was failing when tested using row based
binlog format.

While analyzing the issue it was found the following issues:

a) The server is calling binlog related code even when a statement will
   not be binlogged;
b) The child table list was not present into table structure by the time
   to generate the create table statement;
c) The tables in the child table list will not be opened yet when
   generating table create info using row based replication;
d) CREATE TABLE LIKE TEMP_TABLE does not preserve original table storage
   engine when using row based replication;

This patch addressed all above issues.

@ sql/sql_class.h

Added a function to determine if the binary log is disabled to
  the current session. This is related with issue (a) above.

@ sql/sql_table.cc

Added code to skip binary logging related code if the statement
  will not be binlogged. This is related with issue (a) above.

Added code to add the children to the query list of the table that
  will have its CREATE TABLE generated. This is related with issue (b)
  above.

Added code to force the storage engine to be generated into the
  CREATE TABLE. This is related with issue (d) above.

@ storage/myisammrg/ha_myisammrg.cc

Added a test to skip a table getting info about a child table if the
  child table is not opened. This is related to issue (c) above.

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              CONSTRAINT.

Analysis
=======

INSERT and UPDATE operations using the IGNORE keyword which
causes FOREIGN KEY constraint violations reports an error
despite using the IGNORE keyword.

Foreign key violation errors were not ignored and reported
as errors instead of warnings even when IGNORE was set.

Fix
===
Added code to ignore the foreign key violation errors and
report them as warnings when the IGNORE keyword is used.

Fix the following two build warnings so that 5.5 can be compiled
with GCC5.

storage/innobase/dict/dict0crea.c:1143:21: error: logical not is only applied
to the left hand side of comparison [-Werror=logical-not-parentheses]
   ut_a(!node->index == (err != DB_SUCCESS));
                     ^
storage/innobase/log/log0recv.c:1770:20: error: logical not is only applied
to the left hand side of comparison [-Werror=logical-not-parentheses]
  ut_ad(!allow_ibuf == mutex_own(&log_sys->mutex));
                    ^

               ITEM_PARAM::SAFE_CHARSET_CONVERTER

ISSUE:
------
Charset conversion on a null parameter is not handled
correctly.

SOLUTION:
---------
Item_param's charset converter does not handle the case
where it might have to deal with a null value. This is
fine for other charset converters since the value is not
supplied to them at runtime.

The fix is to check if the parameter is now set to null and
return an Item_null object. Also, there is no need to
initialize Item_param's cnvitem in the constructor to a
string. This can be done in
ITEM_PARAM::SAFE_CHARSET_CONVERTER itself.

Members of Item_param, cnvbuf and cnvstr, have been removed
and cnvitem has been made a local variable in
ITEM_PARAM::SAFE_CHARSET_CONVERTER.

'SYSTEM LOCK' IN PROCESSLIST

Analysis
=========
Show processlist shows 'System Lock' in 'State' field while
LOAD DATA INFILE is running.

thd->proc_info update is missing in LOAD DATA INFILE path.
Thus any request will get last unpdated status from lock_table()
during open_table().

Fix:
=======
Update state information from LOAD DATA INFILE path.

    Enable mysqld service by default in sysv initscrips

Go back to __sync_* operations in TAS on x86.

Patch is reviewed by Sunny over IM.

Post-push fix: The problem was that condition variable
timeouts could in some cases (slow machines and/or short
timeouts) be infinite.

When the number of milliseconds to wait is computed, the
end time is computed before the now() time. This can result
in the now() time being later than the end time, leading to
negative timeout. Which after conversion to unsigned becomes
~infinite.

This patch fixes the problem by explicitly checking if we
get negative timeout and then using 0 if this is the case.

Post push fix for 5.5 and 5.6.Disabled the test code due to Bug#22587377

Problem:
mysql-test/suite/rpl/t/rpl_killed_ddl.test

This test contains code which was disabled because of certain bugs.
BUG#44041 declared to be a duplicate of Bug#45516 which was fixed 2010
BUG#43353 fixed 2012
BUG#44171 fixed 2010

Fix:
Enabled the test code related to the above mentioned bugs.

              GENERATED BY THE EXP() FUNCTION

When generating the error message for numeric overflow, pass a flag to
Item::print() that prevents it from expanding constant expressions and
parameters to the values they evaluate to.

For consistency, also pass the flag to Item::print() when
Item_func_spatial_collection::fix_length_and_dec() generates an error
message. It doesn't make any difference at the moment, since constant
expressions haven't been evaluated yet when this function is called.

we can see from the hang stacktrace, srv_monitor_thread is blocked
when getting log_sys::mutex, so that sync_arr_wake_threads_if_sema_free
cannot get a change to break the mutex deadlock.

The fix is simply removing any mutex wait in srv_monitor_thread.

Patch is reviewed by Sunny over IM.

we can see from the hang stacktrace, srv_monitor_thread is blocked
when getting log_sys::mutex, so that sync_arr_wake_threads_if_sema_free
cannot get a change to break the mutex deadlock.

The fix is simply removing any mutex wait in srv_monitor_thread.

Patch is reviewed by Sunny over IM.

Test fix for 5.5 and 5.6

Test Fix

               PROCEDURE RESULTS IN GARBAGE BYTES

Issue:
-----
This problem occurs under the following conditions:

a) Stored procedure has a variable is declared as TEXT/BLOB.
b) Data is copied into the the variable using the
   SELECT...INTO syntax from a TEXT/BLOB column.

Data corruption can occur in such cases.

SOLUTION:
---------
The blob type does not allocate space for the string to be
stored. Instead it contains a pointer to the source string.
Since the source is deallocated immediately after the
select statement, this can cause data corruption.

As part of the fix for Bug #21143080, when the source was
part of the table's write-set, blob would allocate the
neccessary space. But this fix missed the possibility that,
as in the above case, the target might be a variable.

The fix will add the copy_blobs check that was removed by
the earlier fix.

Problem Statement
=========
Fix various issues when building MySQL with Visual Studio 2015.

Fix:
=======
- Visual Studio 2015 adds support for timespec. Add check and
  related code to use this and only use our replacement if
  timespec is not defined.
- Rename lfind/lsearch to my* to avoid redefinition problems.
- Set default value for TMPDIR to "" on Windows as P_tmpdir
  no longer exists.
- using VS definition of snprintf if available
- tzname are now renamed to _tzname.

one leading zeros for the key agreement instead of
potentially any number.
There is about 1 in 50,000 connections to fail
when using DHE cipher suites.  The second problem was the
case where a server would send a public value shorter than
the prime value, causing about 1 in 128 client connections
to fail, and also caused the yaSSL client to read off the
end of memory.
All client side DHE cipher suite users should update.
Note: The patch is received from YaSSL people

               UNIX_TIMESTAMP(STR_TO_DATE('201506', "%Y%M"

Issue:
-----
When an invalid date is supplied to the UNIX_TIMESTAMP
function from STR_TO_DATE, no check is performed before
converting it to a timestamp value.

SOLUTION:
---------
Add the check_date function and only if it succeeds,
proceed to the timestamp conversion.

No warning will be returned for dates having zero in
month/date, since partial dates are allowed. UNIX_TIMESTAMP
will return only a zero for such values.

The problem has been handled in 5.6+ with WL#946.

               COLUMNS

ANALYSIS:
=========
A valgrind error is reported when CREATE TABLE .. SELECT
involving BIT columns triggers a column type redefinition.

In general the pack_flag is set for BIT columns in
'mysql_prepare_create_table()'. However, during the above
operation, redefined column types was handled after the
special handling for BIT columns and thus pack_flag ended
up not being set correctly triggering the valgrind error.

FIX:
====
The patch fixes this problem by setting pack_flag correctly
for BIT columns in the case of column type redefinition.

If the configuration files contains multiple datadir lines, use the last datadir
entry in the RPM installation scripts