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.
sql/item_func.h:
Add constructors.
sql/sql_select.cc:
Change user variable assignment functions to read from fields after
tables have been unlocked.
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
sql/my_decimal.h:
Added constructor and assignment operators for my_decimal
unittest/my_decimal/my_decimal-t.cc:
Added test to check constructor and assignment operators for my_decimal
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
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+).
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.
sql/item_func.h:
Add constructors.
sql/sql_select.cc:
Change user variable assignment functions to read from fields after
tables have been unlocked.
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.
sql/item_subselect.cc:
use left_expr->real_item() instead of original left expression
because left_expr can be runtime created Ref item which is deleted
at the end of the statement. Thus one of 'substitution' arguments
can be broken in case of PS.
Bug #16754901 PARS_INFO_FREE NOT CALLED IN DICT_CREATE_ADD_FOREIGN_TO_DICTIONARY
Problem:
There are two situations here. The constraint name is explicitly
given by the user and the constraint name is automatically generated
by InnoDB. In the case of generated constraint name, it is formed by
adding table name as prefix. The table names are stored internally in
my_charset_filename. In the case of constraint name explicitly given
by the user, it is stored in UTF8 format itself. So, in some
situations the constraint name is in utf8 and in some situations it is
in my_charset_filename format. Hence this problem.
Solution:
Always store the foreign key constraint name in UTF-8 even when
automatically generated.
Bug #16754901 PARS_INFO_FREE NOT CALLED IN DICT_CREATE_ADD_FOREIGN_TO_DICTIONARY
Problem:
There was a memory leak in the function dict_create_add_foreign_to_dictionary().
The allocated pars_info_t object is not freed in the error code path.
Solution:
Allocate the pars_info_t object after the error checking.
rb#2368 in review
eliminate a race condition over recv_sys->n_addrs which might result in a database corruption
in recovery, without reporting a recovery error.
recv_recover_page_func(): move the code segment that decrements recv_sys->n_addrs
to the end of the function, after the call to mtr_commit()
rb://2282 approved by Inaam
GROUP BY, MYISAM
Problem:-
In a query, where we are using loose index scan optimization and
we have MIN() causes segmentation fault(where table row length
is less then key_length).
Analysis:
While using loose index scan for MIN(), we call key_copy(), to copy
the key data from record.
This function is using temporary record buffer to store key data
from the record buffer.But in case where the key length is greater
then the buffer length, this will cause a segmentation fault.
Solution:
Give a proper buffer to store a key record.
sql/opt_range.cc:
We can't use record buffer to store key data.So, give a proper buffer to store a key record.
OPENING MISSING PARTITION
In the ha_innobase::open() call, for normal tables, there is no retry logic.
But for partitioned tables, there is a retry logic introduced as fix for:
http://bugs.mysql.com/bug.php?id=33349https://support.mysql.com/view.php?id=21080
The Bug#33349, does not provide sufficient information to analyze the original
problem. The original problem reported by bug#33349 is also minor (just an
annoyance and no loss of functionality). Most importantly, the retry logic
has been introduced without any associated test case.
So we are removing the retry logic for partitioned tables. When the original
problem occurs, a different solution will be explored.
Problem:
In query like
select 1 from .. order by match .. against ...;
causes a debug assert failue.
Analysis:
In union type query like
(select * from order by a) order by b;
or
(select * from order by a) union (select * from order by b);
We skip resolving of order by a for 1st query and order by of a and b in
2nd query.
This means that, in case when our order by have Item_func_match class,
we skip resolving it.
But we maintain a ft_func_list and at the time of optimization, when we
Perform FULLTEXT search before all regular searches on the bases of the
list we call Item_func_match::init_search() which will cause debug assert
as the item is not resolved.
Solution:
We will skip execution if the item is not fixed and we will not
fix index(Item_func_match::fix_index()) for which
Item_func_match::fix_field() is not called so that on later changes
we can check the dependency on fix field.
sql/item_func.cc:
skiping execution, if item is not resolved.
!TABLES->NEXT_NAME_RESOLUTION_TABLE) || !TAB
Problem:
The context info of select query gets corrupted when a query
with group_concat having order by is present in an order by
clause of the select query. As a result, server crashes with
an assert.
Analysis:
While parsing order by for group_concat, it is presumed that
it is always present before the actual order by for the
select query.
As a result, parser uses select->order_list to populate the
order by items of group_concat and creates a select->gorder_list
to which select->order_list is copied onto. Once this is done,
it empties the select->order_list.
In the case presented in the bugpage, as order by is already
parsed when group_concat's order by is encountered, parser
presumes that it is the second order by in the select query
and creates fake_lex_unit which results in the change of
context info.
Solution:
Make group_concat's order by parsing independent of the select
sql/item_sum.cc:
Change the argument as, select->gorder_list is not pointer anymore
sql/item_sum.h:
Change the argument as, select->gorder_list is not pointer anymore
sql/mysql_priv.h:
Parsing for group_concat's order by is made independent.
As a result, add_order_to_list cannot be used anymore.
sql/sql_lex.cc:
Parsing for group_concat's order by is made independent.
As a result, add_order_to_list cannot be used anymore.
sql/sql_lex.h:
Parsing for group_concat's order by is made independent.
As a result, add_order_to_list cannot be used anymore.
sql/sql_yacc.yy:
Make group_concat's order by parsing independent of the select
queries order by.
Problem:
A select query inside a group_concat function having an
outer reference results in a crash.
Analysis:
In function Item_group_concat::add, we do not check if
return value of get_tmp_table_field can be NULL for
a non-const item. This can happen for a query with a
outer reference.
While resolving the outer reference in the query present
inside group_concat function, we set the "const_item_cache"
to false. As a result in the call to const_item() from
Item_func_group_concat::add, it returns false and goes on
to check if this can be NULL resulting in the crash.
get_tmp_table_field does not return NULL for Items of type
Item_field, Item_result_field and Item_ref.
For all other items, it returns NULL.
Solution:
Check for the return value of get_tmp_table_field before we
access field contents.
sql/item_sum.cc:
Check for the return value of get_tmp_table_field before accessing
TABLE/KEY RELATIONS
The DICT_FK_MAX_RECURSIVE_LOAD was reduced from 250 to 33 in rb#2058.
But in optimized build, this recursive depth is still too deep and
resulted in stack overflow. So reducing this depth to 20 now.
Fixed the get_data_size() methods for multi-point features to check properly for end
of their respective data arrays.
Extended the point checking function to take a 3d optional argument so cases where
there's additional data in each array element (besides the point data itself) can be
covered by the helper function.
Fixed the 3 cases where such offset was present to use the proper checking helper
function.
Test cases added.
Fixed review comments.
REGULAR SQL VS PREPARED STATEMENT
Analysis:
---------
When passing user variables as parameters to the
prepared statements, the IF() function evaluation
turns out to be incorrect.
Consider the example:
SET @var1='0.038687';
SELECT @var1 , IF( @var1 = 0 , 1 ,@var1 ) AS sqlif ;
+----------+----------+
| @var1 | sqlif |
+----------+----------+
| 0.038687 | 0.038687 |
+----------+----------+
Executing a prepared statement where the parameters are
supplied:
PREPARE fail_stmt FROM "SELECT ? ,
IF( ? = 0 , 1 , ? ) AS ps_if_fail" ;
EXECUTE fail_stmt USING @var1 ,@var1 , @var1 ;
+----------+------------+
| ? | ps_if_fail |
+----------+------------+
| 0.038687 | 1 |
+----------+------------+
1 row in set (0.00 sec)
In the regular statement or while executing the prepared
statements without passing parameters, the decimal
precision is set for the user variable of type string.
The comparison function used for evaluation considered
the precision while comparing the values.
But while executing the prepared statement with the
parameters supplied, the decimal precision was not
set. Thus the comparison function chosen was different
which looked at the absolute values for comparison.
Fix:
----
The fix is to set 'decimals' field of Item_param to the
default value which is nothing but the maximum number of
decimals(NOT_FIXED_DEC). This is set for cases where the
strings are converted to the numeric form within certain
functions. Thus the value is not rounded off during
comparison, ensuring correct evaluation.
NO ERRORS REPORTED
Problem:
=======
Errors from my_b_fill are ignored. MYSQL_BIN_LOG::write_cache
code assumes that 0 returned from my_b_fill always means
end-of-cache, but that is incorrect. It can result in error
and the error is ignored. Other callers of my_b_fill don't
check for error: my_b_copy_to_file, maybe my_b_gets.
Fix:
===
An error handler is already present to check the "cache"
error that is reported during "MYSQL_BIN_LOG::write_cache"
call. Hence error handlers are added for "my_b_copy_to_file"
and "my_b_gets".
During my_b_fill() function call, when the cache read fails
info->error= -1 is set. Hence a check for "info->error"
is added for the above to callers upon their return.
mysys/mf_iocache2.c:
Added a check for "cache->error" and simulation of cache read failure
mysys/my_read.c:
Simulation of read failure
sql/log_event.cc:
Added debug simulation
sql/sql_repl.cc:
Added a check for cache error
TABLE/KEY RELATIONS
Problem:
When there are many tables, linked together through the foreign key
constraints, then loading one table will recursively open other tables. This
can sometimes lead to thread stack overflow. In such situations the server
will exit.
I see the stack overflow problem when the thread_stack is 196608 (the default
value for 32-bit systems). I don't see the problem when the thread_stack is
set to 262144 (the default value for 64-bit systems).
Solution:
Currently, in InnoDB, there is a macro DICT_FK_MAX_RECURSIVE_LOAD which defines
the maximum number of tables that will be loaded recursively because of foreign
key relations. This is currently set to 250. We can reduce this number to 33
(anything more than 33 does not solve the problem for the default value). We
can keep it small enough so that thread stack overflow does not happen for the
default values. Reducing the DICT_FK_MAX_RECURSIVE_LOAD will not affect the
functionality of InnoDB. The tables will eventually be loaded.
rb#2058 approved by Marko
The GIS WKB reader was checking for the presence of
enough data by first multiplying the number read (where
it could overflow) and only then comparing it to the
number of bytes available.
This can overflow and effectively turn off the check.
Fixed by:
1. Introducing a new function that does division only so
no overflow is possible.
2. Using the proper macros and parenthesizing them.
3. Doing an in-line division check in the only place where
the boundary check is done over a data structure other
than a dense points array.
--BINLOG-IGNORE-DB AND FULLY QUALIFIED TABLE
Problem:
=======
An ALTER TABLE statement is not written to binlog if server
started with "--binlog-ignore-db some database" and 'fully
qualified' table names are used in the ALTER TABLE statement
altering table different from current database context.
Analysis:
========
The above mentioned problem not only affects "ALTER TABLE"
statements but also to all kind of statements. Once the
current default database becomes "NULL" none of the
statements will be binlogged.
The current behaviour is such that if the user has specified
restrictions on which database needs to be replicated and the
default db is not specified, then do not replicate.
This means that "NULL" is considered to be equivalent to
everything (default db = null implied ignore don't log the
statement).
Fix:
===
"NULL" should not be considered as equivalent to everything.
Since the filtering criteria is not equal to "NULL" the
statement should be logged into binlog.
mysql-test/suite/rpl/r/rpl_loaddata_m.result:
Earlier when defalut database was "NULL" DROP TABLE
was not getting logged. Post this fix it will be logged
and the DROP will fail at slave as the table creation
was skipped by master as --binlog-ignore-db=test.
mysql-test/suite/rpl/t/rpl_loaddata_m.test:
Earlier when defalut database was "NULL" DROP TABLE
was not getting logged. Post this fix it will be logged
and the DROP will fail at slave as the table creation
was skipped by master as --binlog-ignore-db=test.
sql/rpl_filter.cc:
Replaced DBUG_RETURN(0) with DBUG_RETURN(1).
At logging a first Query referring a user var, the slave missed to log the user var.
It appears that at execution of a Uservar event the slaver applier
thought of the variable as already logged.
The reason of misjudgement is in coincidence of query id:s: of one that the thread
holds at Uservar execution and another one that the thread sees at the Query applying.
While the two are naturally different in the regular execution branch (as two computational
events are separated as individual events), in the deferred applying case the User var execution
effectively belongs to its Query processing.
Fixed with storing the Uservar parsing time (where desicion to defer is taken) query id
to temporarily substitute with it the actual query id at the Uservar execution time
(along with its query).
Such manipulation mimics behaviour of the regular applying branch.
sql/log_event.cc:
Storing the Uservar parsing time query id into a new member of the event
to to temporarily substitute
with it the actual thread id at the Uservar execution time.
sql/log_event.h:
Storage for keeping query-id in User-var intance is added.
Bug#13243248 CHECK FOR "STACK OVERRUN" DOESN'T WORK WITH GCC-4.6, SERVER CRASHES
The existing check for stack direction may give wrong results
for new versions of gcc at high optimization levels.
Solution: Backport the stack-direction check from 5.5
As current size limit of 'url' field of help_topic
table is no longer sufficient for the contents of
the fill_help_tables-5.1.sql. So, loading the contents
in the table might result in warning (or error with
stricter modes).
Updated the type for 'url' field of help_topic as well
as help_category tables from char(128) to text.
Problem:
=======
Found using AddressSanitizer testing.
The mysqlbinlog utility may result in out-of-bound heap
buffer reads and thus, undefined behaviour, when processing
RBR events in the old (pre-5.1 GA) format.
The following code in process_event() would only be correct
if Rows_log_event was the base class for
Write,Update,Delete_rows_log_event_old classes:
case PRE_GA_WRITE_ROWS_EVENT:
case PRE_GA_DELETE_ROWS_EVENT:
case PRE_GA_UPDATE_ROWS_EVENT:
...
Rows_log_event *e= (Rows_log_event*) ev;
Table_map_log_event *ignored_map=
print_event_info->m_table_map_ignored.get_table(e->get_table_id());
...
if (e->get_flags(Rows_log_event::STMT_END_F))
{
...
}
However, Rows_log_event is only the base class for the
Write,Update_Delete_rows_event family of classes, but not
for their *_old counterparts. So the above typecasts are
incorrect for the old-format RBR events and may result (and
do result according to AddressSanitizer reports) in reading
memory outside of the previously allocated on heap buffer.
Fix:
===
The above mentioned invalid type cast has been replaced with
appropriate old counterpart.
Note:The above mentioned issue is present only mysql-5.1 and
5.5. This is fixed in mysql-5.6 and above as part of
Bug#55790. Hence few of the relevant changes of Bug#55790 are
being back ported to fix the current issue.
client/mysqlbinlog.cc:
The above mentioned invalid type cast of using new event
object to read old events, has been replaced with
appropriate old counterpart.
Note:The above mentioned issue is present only mysql-5.1 and
5.5. This is fixed in mysql-5.6 and above as part of
Bug#55790. Hence few of the relevant changes of Bug#55790 are
being back ported to fix the current issue.
INTERACTIVE MODE
In interactive mode, libedit/readline allocates memory
for every new line entered & later the allocated memory
never gets freed.
Fixed by freeing the allocated memory blocks appropriately.
