streamline the event worker thread work flow and try to eliminate
possibilities for memory corruptions that might have been
lurking in previous (complicated) code.
This patch:
* removes Event_job_data::compile that was never used
* cleans up Event_job_data::execute to minimize juggling with
thread context and eliminate unneded code paths
* Implements Security_context::change/restore_security_context
to be able to re-use these methods in all stored programs
This is to maybe fix Bug#27733 "Valgrind failures in
remove_table_from_cache".
Review comments applied.
Print information if net_clear() skipped bytes (As this otherwise hides critical timeing bugs)
Added DBUG_ASSERT if we get packets out of order
mysql_change_user() could on error send multiple packets, which caused mysql_client_test to randomly fail
skipped):
By moving statement end actions from Rows_log_event::do_apply_event() to
Rows_log_event::do_update_pos() they will always be executed, even if
Rows_log_event::do_apply_event() is skipped because the event originated
at the same server. This because Rows_log_event::do_update_pos() is always
executed (unless Rows_log_event::do_apply_event() failed with an error,
in which case the slave stops with an error anyway).
Adding test case.
Fixing logic to detect if inside a group. If a rotate event occured
when an initial prefix of events for a statement, but for which the
table did contain a key, last_event_start_time is set to zero, causing
rotate to end the group but without unlocking any tables. This left a
lock hanging around, which subsequently triggered an assertion when a
second attempt was made to lock the same sequence of tables.
In order to solve the above problem, a new flag was added to the relay
log info structure that is used to indicate that the replication thread
is currently executing a statement. Using this flag, the replication
thread is in a group if it is either in a statement or inside a trans-
action.
The patch also eliminates some gratuitous header file inclusions that
were not needed (and caused compile errors) and replaced them with
forward definitions.
Problem: setting/displaying @@LC_TIME_NAMES didn't distinguish between
GLOBAL and SESSION variable types - always SESSION variable
was set/shonw.
Fix: set either global or session value.
Also, "mysqld --lc-time-names" was added to set "global default" value.
- Problem: data separators were copied to a fixed-size buffer
on the stack; memcpy was used, without bounds checking; a
server crash could result if long FIELDS ENCLOSED BY, etc.,
was given
- Fix: write the separators directly, instead of copying to
a buffer first (in select_export::send_data())
Field_bit::pack() and Field_bit::unpack() does not work correctly
Fixing code for Field_bit packing and unpacking to work with arbitrary
pointers instead of requiring Field::ptr
When rand() is called multiple times inside a stored procedure, the server does
not binlog the correct random seed values.
This patch corrects the problem by resetting rand_used= 0 in
THD::cleanup_after_query() allowing the system to save the random seeds if needed
for each command in a stored procedure body.
However, rand_used is not reset if executing in a stored function or trigger
because these operations are binlogged by call and thus only the calling statement
need detect the call to rand() made by its substatements. These substatements must
not set rand_used to 0 because it would remove the detection of rand() by the
calling statement.
fixes).
The legend: on a replication slave, in case a trigger creation
was filtered out because of application of replicate-do-table/
replicate-ignore-table rule, the parsed definition of a trigger was not
cleaned up properly. LEX::sphead member was left around and leaked
memory. Until the actual implementation of support of
replicate-ignore-table rules for triggers by the patch for Bug 24478 it
was never the case that "case SQLCOM_CREATE_TRIGGER"
was not executed once a trigger was parsed,
so the deletion of lex->sphead there worked and the memory did not leak.
The fix:
The real cause of the bug is that there is no 1 or 2 places where
we can clean up the main LEX after parse. And the reason we
can not have just one or two places where we clean up the LEX is
asymmetric behaviour of MYSQLparse in case of success or error.
One of the root causes of this behaviour is the code in Item::Item()
constructor. There, a newly created item adds itself to THD::free_list
- a single-linked list of Items used in a statement. Yuck. This code
is unaware that we may have more than one statement active at a time,
and always assumes that the free_list of the current statement is
located in THD::free_list. One day we need to be able to explicitly
allocate an item in a given Query_arena.
Thus, when parsing a definition of a stored procedure, like
CREATE PROCEDURE p1() BEGIN SELECT a FROM t1; SELECT b FROM t1; END;
we actually need to reset THD::mem_root, THD::free_list and THD::lex
to parse the nested procedure statement (SELECT *).
The actual reset and restore is implemented in semantic actions
attached to sp_proc_stmt grammar rule.
The problem is that in case of a parsing error inside a nested statement
Bison generated parser would abort immediately, without executing the
restore part of the semantic action. This would leave THD in an
in-the-middle-of-parsing state.
This is why we couldn't have had a single place where we clean up the LEX
after MYSQLparse - in case of an error we needed to do a clean up
immediately, in case of success a clean up could have been delayed.
This left the door open for a memory leak.
One of the following possibilities were considered when working on a fix:
- patch the replication logic to do the clean up. Rejected
as breaks module borders, replication code should not need to know the
gory details of clean up procedure after CREATE TRIGGER.
- wrap MYSQLparse with a function that would do a clean up.
Rejected as ideally we should fix the problem when it happens, not
adjust for it outside of the problematic code.
- make sure MYSQLparse cleans up after itself by invoking the clean up
functionality in the appropriate places before return. Implemented in
this patch.
- use %destructor rule for sp_proc_stmt to restore THD - cleaner
than the prevoius approach, but rejected
because needs a careful analysis of the side effects, and this patch is
for 5.0, and long term we need to use the next alternative anyway
- make sure that sp_proc_stmt doesn't juggle with THD - this is a
large work that will affect many modules.
Cleanup: move main_lex and main_mem_root from Statement to its
only two descendants Prepared_statement and THD. This ensures that
when a Statement instance was created for purposes of statement backup,
we do not involve LEX constructor/destructor, which is fairly expensive.
In order to track that the transformation produces equivalent
functionality please check the respective constructors and destructors
of Statement, Prepared_statement and THD - these members were
used only there.
This cleanup is unrelated to the patch.
