DO WHAT YOU EXPECT"

Fix info:
--------

Backport of the deprecation bug fix (WL#5265) for global variable
'THREAD_CONCURRENCY' from mysql-5.6 to mysql-5.5

Note: With this backport, certain additional deprecation warnings
      would be reported under error conditions while setting the
      global/session variables.

	       CONTAINING NULL

Problem:-
In MySQL, We can obtain the number of distinct expression
combinations that do not contain NULL by giving a list of 
expressions in COUNT(DISTINCT).
However rows with NULL values are
incorrectly included in the count when loose index scan is 
used.

Analysis:-
In case of loose index scan, we check whether the field is null or 
not and increase the count in Item_sum_count::add().
But there we are checking for the first field in COUNT(DISTINCT), 
not for every field. This is causing an incorrect result.

Solution:-
Check all field in Item_sum_count::add(), whether there values 
are null or not. Then only increment the count.
******
Bug#17222452 - SELECT COUNT(DISTINCT A,B) INCORRECTLY COUNTS ROWS 
	       CONTAINING NULL

Problem:-
In MySQL, We can obtain the number of distinct expression
combinations that do not contain NULL by giving a list of 
expressions in COUNT(DISTINCT).
However rows with NULL values are
incorrectly included in the count when loose index scan is 
used.

Analysis:-
In case of loose index scan, we check whether the field is null or 
not and increase the count in Item_sum_count::add().
But there we are checking for the first field in COUNT(DISTINCT), 
not for every field. This is causing an incorrect result.

Solution:-
Check all field in Item_sum_count::add(), whether there values 
are null or not. Then only increment the count.

              SPECIFIED WITH THE BASEDIR OPTION

Description: The mysql_plugin client attempts to remove any
filename specified to the --basedir option. The problem is 
that if the filename does not end with a slash, it will 
attempt to unlink it, which succeeds for files, but not for 
directories.

Analysis: When we are starting mysql_plugin with basedir 
option and if we are giving path of a file as basedir, it 
deletes that file. It was because it uses a function 
my_delete which unlinks the file path given.

Fix:  As a fix we replace that line using another function 
my_free, which will only free the  pointer which is having 
that file path.

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Memory Leak in mysql_options() was caused by missing call
to my_free() in MYSQL_SET_CLIENT_IP branch. Fixed by adding
my_free() to cleanup mysql->options.client_ip value before
assigning new value.

Memory Leak in mysql_options() was caused by missing call
to my_free() in MYSQL_SET_CLIENT_IP branch. Fixed by adding
my_free() to cleanup mysql->options.client_ip value before
assigning new value.

             ERROR HANDLING CODE 

BACKGROUND:
There can be a potential crash due to buffer overrun in 
SSL error handling code due to missing comma in
ssl_error_string[] array in viosslfactories.c.

ANALYSIS:
Found by code Inspection.

FIX:
Added the missing comma in SSL error handling code
in ssl_error_string[] array in viosslfactories.c.

             ERROR HANDLING CODE 

BACKGROUND:
There can be a potential crash due to buffer overrun in 
SSL error handling code due to missing comma in
ssl_error_string[] array in viosslfactories.c.

ANALYSIS:
Found by code Inspection.

FIX:
Added the missing comma in SSL error handling code
in ssl_error_string[] array in viosslfactories.c.

Problem:-
Second execution of prepared statement for query with 
parameter in limit clause, causes an assert when using 
connectors (e.g., Connector C).  


Analysis:-
In prepared statement, LIMIT parameters can be
specified using '?' markers. Value for the parameter can
be supplied while executing the prepared statement.

Passing string, float or double values for LIMIT clause
works well from command-line client. That's because, while 
setting the LIMIT parameter value from a user-variable,
the value is converted to integer value.

However, when prepared statement is executed from other
interfaces as J connectors, or C applications etc,
the value for the parameters are sent to the server
with execute command. Each item in command has value and
the data TYPE. So, while setting parameter values
from this log, value is set to all the parameters
with the same data type as passed.
Here, we have the logic to convert the value to change the 
state and item_type if it is part of LIMIT parameter and 
its item_type is not INT.
But when we reset this parameter we save the item_type but change 
state. So on second execution we have old item_type but our state 
has been changed, which make us to use string type variable 
in Item_param::query_str_val(). This cause an assert.

Fix:
Instead of checking the item_type of the parameter, check for 
the state of the parameter. As state value are reset everytime
we execute the statement.

ER_LOCK_WAIT_TIMEOUT".

The problem was that after changes caused by fix bug 14188793 "DEADLOCK
CAUSED BY ALTER TABLE DOEN'T CLEAR STATUS OF ROLLBACKED TRANSACTION"/
bug 17054007 "TRANSACTION IS NOT FULLY ROLLED BACK IN CASE OF INNODB
DEADLOCK implicit rollback of transaction which occurred on ER_LOCK_DEADLOCK
(and ER_LOCK_WAIT_TIMEOUT if innodb_rollback_on_timeout option was set)
didn't start new transaction in @@autocommit=1 mode.

Such behavior although consistent with behavior of explicit ROLLBACK has
broken expectations of users and backward compatibility assumptions.

This patch fixes problem by reverting to starting new transaction
in 5.5/5.6.

The plan is to keep new behavior in trunk so the code change from this
patch is to be null-merged there.

               "SHOW PROCESSLIST"

Follow up path, addressing pb2 test failure.

No commit message

Problem:-
In a Procedure, when we are comparing value of select query 
with IN clause and they both have different collation, cause 
error on first time execution and assert second time.
procedure will have query like
set @x = ((select a from t1) in (select d from t2));<---proc1
              sel1                   sel2

Analysis:-
When we execute this proc1(first time)
While resolving the fields of user variable, we will call 
Item_in_subselect::fix_fields while will resolve sel2. There 
in Item_in_subselect::select_transformer, we evaluate the 
left expression(sel1) and store it in Item_cache_* object 
(to avoid re-evaluating it many times during subquery execution) 
by making Item_in_optimizer class.
While evaluating left expression we will prepare sel1.
After that, we will put a new condition in sel2  
in Item_in_subselect::select_transformer() which will compare 
t2.d and sel1(which is cached in Item_in_optimizer).

Later while checking the collation in agg_item_collations() 
we get error and we cleanup the item. While cleaning up we cleaned 
the cached value in Item_in_optimizer object.

When we execute the procedure second time, we have condition for 
sel2 and while setup_cond(), we can't able to find reference item 
as it is cleanup while item cleanup.So it assert.


Solution:-
We should not cleanup the cached value for Item_in_optimizer object, 
if we have put the condition to subselect.

Problem:-
In a Procedure, when we are comparing value of select query 
with IN clause and they both have different collation, cause 
error on first time execution and assert second time.
procedure will have query like
set @x = ((select a from t1) in (select d from t2));<---proc1
              sel1                   sel2

Analysis:-
When we execute this proc1(first time)
While resolving the fields of user variable, we will call 
Item_in_subselect::fix_fields while will resolve sel2. There 
in Item_in_subselect::select_transformer, we evaluate the 
left expression(sel1) and store it in Item_cache_* object 
(to avoid re-evaluating it many times during subquery execution) 
by making Item_in_optimizer class.
While evaluating left expression we will prepare sel1.
After that, we will put a new condition in sel2  
in Item_in_subselect::select_transformer() which will compare 
t2.d and sel1(which is cached in Item_in_optimizer).

Later while checking the collation in agg_item_collations() 
we get error and we cleanup the item. While cleaning up we cleaned 
the cached value in Item_in_optimizer object.

When we execute the procedure second time, we have condition for 
sel2 and while setup_cond(), we can't able to find reference item 
as it is cleanup while item cleanup.So it assert.


Solution:-
We should not cleanup the cached value for Item_in_optimizer object, 
if we have put the condition to subselect.

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         in 5.5, 5.6, 5.7.

THAN LOCALHOST

      This is a test bug and the explanation for the behaviour can be found
on the bug page.Modifying the select to select user where user!=root for the line where
failure is encountered on machines with no hostname other than the localhost.

compressed pages

After loading a compressed-only page in buf_page_get_gen() we allocate a new
block for decompression. The problem is that the compressed page is neither
buffer-fixed nor I/O-fixed by the time we call buf_LRU_get_free_block(),
so it may end up being evicted and returned back as a new block.

buf_page_get_gen(): Temporarily buffer-fix the compressed-only block
while allocating memory for an uncompressed page frame.
This should prevent this form of the infinite loop, which is more likely
with a small innodb_buffer_pool_size.

rb#2511 approved by Jimmy Yang, Sunny Bains

               "SHOW PROCESSLIST"

Merging from 5.1 to 5.5

               "SHOW PROCESSLIST"

Analysis:
----------
The problem here is, if one connection changes its
default db and at the same time another connection executes
"SHOW PROCESSLIST", when it wants to read db of the another
connection then there is a chance of accessing the invalid
memory. 

The db name stored in THD is not guarded while changing user
DB and while reading the user DB in "SHOW PROCESSLIST".
So, if THD.db is freed by thd "owner" thread and if another
thread executing "SHOW PROCESSLIST" statement tries to read
and copy THD.db at the same time then we may endup in the issue
reported here.

Fix:
----------
Used mutex "LOCK_thd_data" to guard THD.db while freeing it
and while copying it to processlist.

STATUS OF ROLLBACKED TRANSACTION" and bug #17054007 - "TRANSACTION
IS NOT FULLY ROLLED BACK IN CASE OF INNODB DEADLOCK".

The problem in the first bug report was that although deadlock involving
metadata locks was reported using the same error code and message as InnoDB
deadlock it didn't rollback transaction like the latter. This caused
confusion to users as in some cases after ER_LOCK_DEADLOCK transaction
could have been restarted immediately and in some cases rollback was
required.

The problem in the second bug report was that although InnoDB deadlock
caused transaction rollback in all storage engines it didn't cause release
of metadata locks. So concurrent DDL on the tables used in transaction was
blocked until implicit or explicit COMMIT or ROLLBACK was issued in the
connection which got InnoDB deadlock.

The former issue has stemmed from the fact that when support for detection
and reporting metadata locks deadlocks was added we erroneously assumed
that InnoDB doesn't rollback transaction on deadlock but only last statement
(while this is what happens on InnoDB lock timeout actually) and so didn't
implement rollback of transactions on MDL deadlocks.

The latter issue was caused by the fact that rollback of transaction due
to deadlock is carried out by setting THD::transaction_rollback_request
flag at the point where deadlock is detected and performing rollback
inside of trans_rollback_stmt() call when this flag is set. And
trans_rollback_stmt() is not aware of MDL locks, so no MDL locks are
released.

This patch solves these two problems in the following way:

- In case when MDL deadlock is detect transaction rollback is requested
  by setting THD::transaction_rollback_request flag.

- Code performing rollback of transaction if THD::transaction_rollback_request
  is moved out from trans_rollback_stmt(). Now we handle rollback request
  on the same level as we call trans_rollback_stmt() and release statement/
  transaction MDL locks.

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