MYSQL DB FROM REMOTE 5.0.96 SERVER

Problem: mysqldump tool assumes the existence of
general_log and slow_log tables in the server.
If mysqldump tool executes on a old server where
there are no log tables like these, mysqldump tool
fails.

Analysis: general_log and slow_log tables are added
in the ignore-table list as part of bug-26121 fix
causes bug-45740 (MYSQLDUMP DOESN'T DUMP GENERAL_LOG
AND SLOW_QUERY CAUSES RESTORE PROBLEM). As part of
the bug-45740 fix, mysqldump tool adds create table
queries for these two tables. But the fix assumes
that on all the servers, general_log and slow_log
will be there. If the new mysqldump tool is executed
against a old server where there are no general_log
and slow_log, the mysqldump tool fails with an error
that 'there is no general_log table'.

Fix: When mysqldump tool is trying to retrieve general_log
and slow_log table structures, first the tool should
check their existence of these tables in the server
instead of trying to dump it blindly.

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The problem was in get_partition_id_cols_range_for_endpoint
and cmp_rec_and_tuple_prune, which stepped one partition too long.

Solution was to move a small portion of logic to cmp_rec_and_tuple_prune,
to simplify both get_partition_id_cols_range_for_endpoint and
get_partition_id_cols_list_for_endpoint.

ibuf_insert_to_index_page_low() add a DBUG_RETURN(NULL).

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.

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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

INNODB_FAST_SHUTDOWN IS 2

Problem:

When innodb_fast_shutdown is set to 2 and the master thread enters
flush loop, under some circumstances it will not be able to exit it.
This may lead to a shutdown hanging.

This is happening because of the following:

1. In the flush_loop block of code, if the srv_fast_shutdown is
   equal to 2 (very fast shutdown), then we do not flush dirty
   pages in buffer pool to disk.
 
2. In the same flush_loop block of code, if the number of dirty
   pages is more than user specified limit, we go to step 1.

This results in infinite loop.

Solution:

When we are in the process of doing a very fast shutdown, don't
do step 2 above.

rb#2328 approved by Inaam.

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

AFTER A ROW IS READ


Approved by: Sunny Bains rb://2425

Don't release concurrency tickets when asked to release
btr_search_latch. This is a 5.5 only bug. It is already
fixed in 5.6 upwards.

No commit message

                           In log_event.h
      
DESCRIPTION:
Due to inclusion of an implementation file, namely 'rpl_tblmap.cc'
in a header file, namely 'log_event.h'; linker errors occur if
log_event.h is included in an application containing multiple source
files, such as in the case of Binlog API.
      
Binlog API requires including log_event.h in its source files;
which leads to multiple definition errors, for functions defined
in rpl_tblmap.cc for class 'table_mapping'.
            
FIX:
Change the inclusion from header file(log_event.h) to source files
using this header and have flag MYSQL_CLIENT set. The only file in
the current server repository is mysqlbinlog.cc.

== Analysis == 
Both change buffer pages and on-disk indexes pages are marked as
FIL_PAGE_INDEX. So all ibuf index pages will classify as INDEX with NULL
table_name and index_name.

== Solution ==
A new page type for ibuf data pages named I_S_PAGE_TYPE_IBUF is defined. All
these pages whose index_id equal (DICT_IBUF_ID_MIN + IBUF_SPACE_ID) will 
classify as IBUF_DATA instead of INDEX in INNODB_BUFFER_PAGE 
and INNODB_BUFFER_PAGE_LRU.

This fix is only for IS reporting, both on-disk and buffer pool structures
keep unchanged.

Approved by both Marko and Jimmy. rb#2334

               WITH COMPOSITE KEY COLUMNS

Problem:-
While running a SELECT query with several AGGR(DISTINCT) function 
and these are referring to different field of same composite key, 
Returned incorrect value.

Analysis:-

In a table, where we have composite key like (a,b,c)
and when we give a query like

select COUNT(DISTINCT b), SUM(DISTINCT a) from ....

here, we first make a list of items in Aggr(distinct) function
(which is a, b), where order of item doesn't matter. 
and then we see, whether we have a composite key where the prefix 
of index columns matches the items of the aggregation function.
(in this case we have a,b,c).

if yes, so we can use loose index scan and we need not perform 
duplicate removal to distinct in our aggregate function.

In our table, we traverse column marked with <-- and get the result as
(a,b,c)      count(distinct b)           sum(distinct a)
             treated as count b          treated as sum(a)
(1,1,2)<--              1                      1		
(1,2,2)<--              1++=2                  1+1=2
(1,2,3)		
(2,1,2)<--              2++=3                  1+1+2=4
(2,2,2)<--              3++=4                  1+1+2+2=6
(2,2,3)

result will be 4,6, but it should be (2,3)

As in this case, our assumption is incorrect. If we have
query like 
select count(distinct a,b), sum(distinct a,b)from ..
then we can use loose index scan

Solution:-
In our query, when we have more then one aggr(distinct) function 
then they should refer to same  fields like

select count(distinct a,b), sum(distinct a,b) from .. 

-->we can use loose scan index as both aggr(distinct) refer to same fields a,b.

If they are referring to different field like

select count(distinct a), sum(distinct b) from .. 

-->will not use loose scan index as both aggr(distinct) refer to different fields.

No commit message

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

is included only in the builtin InnoDB, and it is missed in InnoDB
plugin.  Adding this function in InnoDB plugin as well.

No commit message

              NUMBER ALREADY USED BY 5.6

The problem was that the patch for Bug#13004581 added a new error
message to 5.5. This causes it to use an error number already used
in 5.6 by ER_CANNOT_LOAD_FROM_TABLE_V2. Which means that error
message number stability between GA releases is broken.

This patch fixes the problem by removing the error message and
using ER_UNKNOWN_ERROR instead.

                           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.

The problem happened due to broken left expression in Item_in_optimizer object.
In case of the bug left expression is runtime created Item_outer_ref item which
is deleted at the end of the statement and one of Item_in_optimizer arguments
becomes bad when re-executed. The fix is to use real_item() instead of original
left expression. Note: It feels a bit weird that after preparing, the field is
directly part of the generated Item_func_eq, whereas in execution it is replaced
with an Item_outer_ref wrapper object.

TRANSACTION ROLLBACK

Problem:
=======
"prepare_commit_mutex" is acquired during "innobase_xa_prepare"
and it is freed only in "innobase_commit". After prepare,
if the commit operation fails the transaction is rolled back
but the mutex is not released.

Analysis:
========
During transaction commit process transaction is prepared and
the "prepare_commit_mutex" is acquired to preserve the order
of commit. After prepare write to binlog is initiated.

File: sql/handler.cc
      if (error || (is_real_trans && xid &&
----->             (error= !(cookie= tc_log->log_xid(thd, xid)))))
      {
        ha_rollback_trans(thd, all);

In the above code "tc_log->log_xid" operation fails.

When the write to binlog fails the transaction is rolled back
with out freeing the mutex. A subsequent "INSERT" operation
tries to acquire the same mutex during its commit process
and the server aborts.

Fix:
===
"prepare_commit_mutex" is freed during "innobase_rollback".