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.

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"

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.

DICT_TABLE_GET_FORMAT(CLUST_INDEX->TABLE) >= 1

The function row_sel_sec_rec_is_for_clust_rec() was incorrectly
preparing to compare a NULL column prefix in a secondary index with a
non-NULL column in a clustered index.

This can trigger an assertion failure in 5.1 plugin and later. In the
built-in InnoDB of MySQL 5.1 and earlier, we would apparently only do
some extra work, by trimming the clustered index field for the
comparison.

The code might actually have worked properly apart from this debug
assertion failure. It is merely doing some extra work in fetching a
BLOB column, and then comparing it to NULL (which would return the
same result, no matter what the BLOB contents is).

While the test case involves CHECK TABLE, this could theoretically
occur during any read that uses a secondary index on a column prefix
of a column that can be NULL.

rb#3101 approved by Mattias Jonsson

There was a race condition in the rollback of TRX_UNDO_UPD_DEL_REC.

Once row_undo_mod_clust() has rolled back the changes by the rolling-back
transaction, it attempts to purge the delete-marked record, if possible, in a
separate mini-transaction.

However, row_undo_mod_remove_clust_low() fails to check if the DB_TRX_ID of
the record that it found after repositioning the cursor, is still the same.
If it is not, it means that the record was purged and another record was
inserted in its place.

So, the rollback would have performed an incorrect purge, breaking the
locking rules and causing corruption.

The problem was found by creating a table that contains a unique
secondary index and a primary key, and two threads running REPLACE
with only one value for the unique column, so that the uniqueness
constraint would be violated all the time, leading to statement
rollback.

This bug exists in all InnoDB versions (I checked MySQL 3.23.53).
It has become easier to repeat in 5.5 and 5.6 thanks to scalability
improvements and a dedicated purge thread.

rb#3085 approved by Jimmy Yang

FAILED BLOB WRITE

btr_store_big_rec_extern_fields(): Relax a debug assertion so that
some BLOB pointers may remain zero if an error occurs.

btr_free_externally_stored_field(), row_undo_ins(): Allow the BLOB
pointer to be zero on any rollback.

rb#3059 approved by Jimmy Yang, Kevin Lewis

Problem Description:
A mysqld_safe instance is started. An InnoDB crash recovery begins which takes
few seconds to complete. During this crash recovery process happening, another
mysqld_safe instance is started with the same server startup parameters. Since
the mysqld's pid file is absent during the crash recovery process the second
instance assumes there is no other process and tries to acquire a lock on the
ibdata files in the datadir.  But this step fails and the 2nd instance keeps 
retrying 100 times each with a delay of 1 second. Now after the 100 attempts, 
the server goes down, but while going down it hits the mysqld_safe script's 
cleanup section and without any check it blindly deletes the socket and pid 
files. Since no lock is placed on the socket file, it gets deleted.

Solution:
We create a mysqld_safe.pid file in the datadir, which protects the presence 
server instance resources by storing the mysqld_safe's process id in it. We
place a check if the mysqld_safe.pid file is existing in the datadir. If yes
then we check if the pid it contains is an active pid or not. If yes again,
then the scripts logs an error saying "A mysqld_safe instance is already 
running". Otherwise it will log the present mysqld_safe's pid into the 
mysqld_safe.pid file.

Problem:
=======
It was detected an incorrect behavior of my_strtoll10 function when 
converting strings with numbers in the following format:
"184467440XXXXXXXXXYY"

Where XXXXXXXXX > 737095516 and YY <= 15

Samples of problematic numbers:
"18446744073709551915"
"18446744073709552001"

Instead of returning the larger unsigned long long value and setting overflow
in the returned error code, my_strtoll10 function returns the lower 64-bits 
of the evaluated number and did not set overflow in the returned error code.

Analysis:
========
Once trying to fix bug 16820156, I've found this bug in the overflow check of
my_strtoll10 function.

This function, once receiving a string with an integer number larger than
18446744073709551615 (the larger unsigned long long number) should return the
larger unsigned long long number and set overflow in the returned error code.

Because of a wrong overflow evaluation, the function didn't catch the
overflow cases where (i == cutoff) && (j > cutoff2) && (k <= cutoff3). When
the overflow evaluation fails, the function return the lower 64-bits of the
evaluated number and do not set overflow in the returned error code.

Fix:
===
Corrected the overflow evaluation in my_strtoll10.

Description:
Original fix Bug#11765744 changed mutex to read write lock
to avoid multiple recursive lock acquire operation on 
LOCK_status mutex.  
On Windows, locking read-write lock recursively is not safe. 
Slim read-write locks, which MySQL uses if they are supported by
Windows version, do not support recursion according to their 
documentation. For our own implementation of read-write lock, 
which is used in cases when Windows version doesn't support SRW,
recursive locking of read-write lock can easily lead to deadlock
if there are concurrent lock requests.

Fix:  
This patch reverts the previous fix for bug#11765744 that used
read-write locks. Instead problem of recursive locking for
LOCK_status mutex is solved by tracking recursion level using 
counter in THD object and acquiring lock only once when we enter 
fill_status() function first time. 

             SHUTDOWN IS IN PROGRESS 

PROBLEM
-------
 In the background thread srv_master_thread() we have a 
 a one second delay loop which will continuously monitor
 server activity .If the server is inactive (with out any
 user activity) or in a shutdown state we do some background
 activity like flushing the changes.In the current code
 we are not checking if server is in shutdown state before
 sleeping for one second.

FIX
---
If server is in shutdown state ,then dont go to one second
sleep. 

Problem:

When the user specified foreign key name contains "_ibfk_", InnoDB wrongly
tries to rename it. 

Solution:

When a table is renamed, all its associated foreign keys will also be renamed,
only if the foreign key names are automatically generated.  If the foreign key
names are given by the user, even if it has _ibfk_ in it, it must not be
renamed.

rb#2935 approved by Jimmy, Krunal and Satya

BUG#12535301- SYS_VARS.RPL_INIT_SLAVE_FUNC MISMATCHES IN DAILY-5.5 

Problem:
sys_vars.rpl_init_slave_func test was not recorded after
the last edit. It was disabled on 5.1 after seeing failures
due to the above reason.
No old failures as this suite never ran with pb2 on 5.1

Fix:
Added assert condition after wait for checks.
Recorded test and enabled it.

              TO DUMP DATA FROM MYSQL-5.6

Analysis
--------
Dumping mysql-5.6 data using mysql-5.1/mysql-5.5 'myqldump'
utility fails with a syntax error.

Server system variable 'sql_quote_show_create' which quotes the
identifiers is set in the mysqldump utility. The mysldump utility
of mysql-5.1/mysql-5.5 uses deprecated syntax 'SET OPTION' to set
the 'sql_quote_show_create' option. The support for the syntax is
removed in mysql-5.6. Hence syntax error is reported while taking
the dump.

Fix:
---
Changed the 'mysqldump' code to use the syntax
'SET SQL_QUOTE_SHOW_CREATE' to set the 'sql_quote_show_create'
option. That syntax is supported on mysql-5.1, mysql-5.5 and
mysql-5.6.

NOTE: I have not added an mtr test case since it is difficult
to simulate the condition. Also the syntax may not be further
simplified in the future.

Cleanup test case (left outfile in data dir)

Analysis
--------
The pthread_mutex commit_threads_m was initiliazed but never
used. 

Fix
---
Removing the commit_threads_m mutex from the code base.

[ Approved by Marko rb#2475]

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             TO INCONSISTENCY 

PROBLEM
--------
When we drop a partitoned table , we first gather the
information about partitions in the table from the 
table_name.par file and store it in an internal data 
structure.Then we delete this file and the data in 
the table. If the server crashes  after deleting the
file,then after recovering we cannot access the table
.Even we cannot drop the table ,because drop algorithm
requires par file to read the partition information.


FIX
---
1. We move the part of deleting par file after deleting 
   all the table data from the storage egine.
2. During drop operation if we detect that the par 
   file is missing then we delete the .frm file,since 
   there is no way of recovering without par file.
  
[Approved by Mattias rb#2576 ]   

BY BINLOG_KILLED_SIMULATE.TEST
      
'mysqbinlog' tool creates a temporary file while 
preparing LOAD DATA QUERY. These files needs to be deleted
at the end of the test script otherwise these files are
left out in the daily-run machines, causing
"no space on device issues"
      
Fix: 
Delete them at the end of these test scripts
1) execute mysqlbinlog with --local-load option to
create these files in a specified tmpdir
2) delete the tmpdir at the end of the test script

                                 STRING CONVERSION FUNCTIONS
            
Problem:
While executing the prepared statement, user variable is
set to memory which would be freed at the end of
execution.
If the statement is executed again, valgrind throws
error when accessing this pointer.
                  
Analysis:
                
1. First time when Item_func_set_user_var::check is called,
   memory is allocated for "value" to store the result.
   (In the call to copy_if_not_alloced).
2. While sending the result, Item_func_set_user_var::check
   is called again. But, this time, its called with
   "use_result_field" set to true. 
   As a result, we call result_field->val_str(&value).
3. Here memory allocated for "value" gets freed. And "value"
   gets set to "result_field", with "str_length" being that of
   result_field's.
4. In the call to JOIN::cleanup, result_field's memory gets
   freed as this is allocated in a chunk as part of the
   temporary table which is needed to execute the query.
5. Next time, when execute of the same statement is called,
   "value" will be set to memory which is already freed.
   Valgrind error occurs as "str_length" is positive 
   (set at Step 3)
                  
Note that user variables list is stored as part of the Lex object
in set_var_list. Hence the persistance across executions.
            
Solution:
Patch for Bug#11764371 fixed in mysql-5.6+ fixes this problem 
as well.So backporting the same.
            
In the solution for Bug#11764371, we create another object of 
user_var and repoint it to temp_table's field. As a result while 
deleting the alloced buffer in Step 3, since the cloned object 
does not own the buffer, deletion will not happen.
So at step 5 when we execute the statement second time, the 
original object will be used and since deletion did not happen 
valgrind will not complain about dangling pointer.

Bug#12608543: CRASHES WITH DECIMALS AND STATEMENT NEEDS TO BE REPREPARED ERRORS

Backporting these two fixes to 5.1 
Added unittest to test my_decimal construtor and assignment operators

INSERT BUFFER MERGE

Problem:

When the record is merged from the change buffer to the actual page,
in a particular condition, it is assumed that the deleted rec will
be re-used by the inserted rec.  With this assumption the lock is
restored on the pointer to the deleted rec itself, thinking that
it is pointing to the newly inserted rec.

Solution:

Just before restoring the lock, update the rec pointer to point
to the newly inserted record.  An assert has been added to verify
this.  This assert will fail without the fix and will pass with
the fix.

rb#2449 in review by Marko and Jimmy

In order to keep error message numbers stable between GA releases, we
can not now add a new error message to 5.1/5.5 as this message would get 
a number now used in 5.6.

This patch enforces this by adding a 5.1/5.5 specific check when processing
the error message file. If a new error message is added, building will
abort and report an error.

When a record contains no user data bytes (such as when the PRIMARY
KEY is an empty string and all secondary index fields are NULL or the
empty string), page_zip_decompress() could fail to set the record
heap_no correctly.

page_zip_decompress_node_ptrs(), page_zip_decompress_sec(),
page_zip_decompress_clust(): Set heap_no also at the end of the
compressed data stream.

rb#2448 approved by Jimmy Yang and Inaam Rana

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innobase_convert_to_filename_charset() was by mistake kept within
the conditional compilation of UNIV_COMPILE_TEST_FUNCS.  Now placing
the function out of UNIV_COMPILE_TEST_FUNCS.  Also, removed the
unnecessary log message (as in 5.6+).

Reverting fix for Bug#16119355 in 5.1 as this needs two patches 
from 5.5+ to work for a certain case