This patch corrects a misstake in the test case for bug patch 43658.

There was a race in the test case when the thread id was retrieved from the processlist.
The result was that the same thread id was signalled twice and one thread id wasn't
signalled at all.

The affected platforms appears to be limited to linux.

mysql-test/r/query_cache_debug.result:
  There was a race in the test case when the thread id was retrieved from the processlist.
  The result was that the same thread id was signalled twice and one thread id wasn't
  signalled at all.
mysql-test/t/query_cache_debug.test:
  There was a race in the test case when the thread id was retrieved from the processlist.
  The result was that the same thread id was signalled twice and one thread id wasn't
  signalled at all.

to a test file that guarantees the presence of partition code

Early patch submitted for discussion.

It is possible for more than one thread to enter the condition
in query_cache_insert(), but the condition predicate is to
signal one thread each time the cache status changes between
the following states: {NO_FLUSH_IN_PROGRESS,FLUSH_IN_PROGRESS,
TABLE_FLUSH_IN_PROGRESS}

Consider three threads THD1, THD2, THD3

   THD2: select ... => Got a writer in ::store_query
   THD3: select ... => Got a writer in ::store_query
   THD1: flush tables => qc status= FLUSH_IN_PROGRESS;
                      new writers are blocked.
   THD2: select ... => Still got a writer and enters cond in
                       query_cache_insert
   THD3: select ... => Still got a writer and enters cond in
                       query_cache_insert
   THD1: flush tables => finished and signal status change.
   THD2: select ... => Wakes up and completes the insert.
   THD3: select ... => Happily waiting for better times. Why hurry?

This patch is a refactoring of this lock system. It introduces four new methods:
   Query_cache::try_lock()
   Query_cache::lock()
   Query_cache::lock_and_suspend()
   Query_cache::unlock()

This change also deprecates wait_while_table_flush_is_in_progress(). All threads are
queued and put on a conditional wait. On each unlock the queue is signalled. This resolve
the issues with left over threads. To assure that no threads are spending unnecessary
time waiting a signal broadcast is issued every time a lock is taken before a full
cache flush.

mysql-test/r/query_cache_debug.result:
  * Added test case for bug43758
mysql-test/t/query_cache_debug.test:
  * Added test case for bug43758
sql/sql_cache.cc:
  * Replaced calls to wait_while_table_flush_is_in_progress() with
    calls to try_lock(), lock_and_suspend() and unlock().
  * Renamed enumeration Cache_status to Cache_lock_status.
  * Renamed enumeration items to UNLOCKED, LOCKED_NO_WAIT and LOCKED.
    If the LOCKED_NO_WAIT lock type is used to lock the query cache, other
    threads using try_lock() will fail to acquire the lock.
    This is useful if the query cache is temporary disabled due to 
    a full table flush.
sql/sql_cache.h:
  * Replaced calls to wait_while_table_flush_is_in_progress() with
    calls to try_lock(), lock_and_suspend() and unlock().
  * Renamed enumeration Cache_status to Cache_lock_status.
  * Renamed enumeration items to UNLOCKED, LOCKED_NO_WAIT and LOCKED.
    If the LOCKED_NO_WAIT lock type is used to lock the query cache, other
    threads using try_lock() will fail to acquire the lock.
    This is useful if the query cache is temporary disabled due to 
    a full table flush.

times (ie: 2:16:20).

mysql-test/r/log_tables_debug.result:
  Update test case result.
mysql-test/t/log_tables_debug.test:
  Skip spaces and handle case when a leading zero is not printed.

mysql-test/t/log_tables_debug.test:
  Remove spurious spaces and disable session debugging.

statements missed from general log

A FLUSH LOGS is added to ensure that the log info hits
the file before attempting to process.

mysql-test/t/log_tables_debug.test:
  A FLUSH LOGS is added, and in the event that a match is
  not found, <FILE> is reset and the contents of the log
  file is dumped for debugging purposes.

crashes server!

The problem affects the scenario when index merge is followed by a filesort
and the sort buffer is not big enough for all the sort keys.
In this case the filesort function will read the data to the end through the 
index merge quick access method (and thus closing the cursor etc), 
but will leave the pointer to the quick select method in place.
It will then create a temporary file to hold the results of the filesort and
will add it as a sort output file (in sort.io_cache).
Note that filesort will copy the original 'sort' structure in an automatic
variable and restore it after it's done.
As a result at exiting filesort() we have a sort.io_cache filled in and 
nothing else (as a result of close of the cursors at end of reading data 
through index merge).
Now create_sort_index() will note that there is a select and will clean it up
(as it's been used already by filesort() reading the data in). While doing that
a special case in the index merge destructor will clean up the sort.io_cache,
assuming it's an output of the index merge method and is not needed anymore.
As a result the code that tries to read the data back from the filesort output 
will get no data in both memory and disk and will crash.
      
Fixed similarly to how filesort() does it : by copying the sort.io_cache structure
to a local variable, removing the pointer to the io_cache (so that it's not freed 
by QUICK_INDEX_MERGE_SELECT::~QUICK_INDEX_MERGE_SELECT) and restoring the original 
structure (together with the valid pointer) after the cleanup is done.
This is a safe thing to do because all the structures are already cleaned up by
hitting the end of the index merge's read method (QUICK_INDEX_MERGE_SELECT::get_next()) 
and the cleanup code being written in a way that tolerates repeating cleanups.

mysql-test/r/index_merge.result:
  Bug #44810: test case
mysql-test/t/index_merge.test:
  Bug #44810: test case
sql/sql_select.cc:
  Bug #44810: preserve the io_cache produced by filesort while cleaning up
  the index merge quick access method (QUICK_INDEX_MERGE_SELECT).

The SQL-mode PAD_CHAR_TO_FULL_LENGTH could prevent a DROP USER
statement from privileges associated with the user being dropped.
What ocurred was that reading from the User and Host fields of
the tables tables_priv or columns_priv would yield values padded
with spaces, causing a failure to match a specified user or host 
('user' != 'user     ');

The solution is to disregard the PAD_CHAR_TO_FULL_LENGTH mode
when iterating over and matching values in the privileges tables
for a DROP USER statement.

mysql-test/r/sql_mode.result:
  Add test case result for Bug#45100.
mysql-test/t/sql_mode.test:
  Add test case for Bug#45100.
sql/sql_acl.cc:
  Clear MODE_PAD_CHAR_TO_FULL_LENGTH before dropping privileges.

statements missed from general log

A refinement of the test in the previous patch to avoid
using sleep as a means to ensure that timestamps are
added to the log entries.

mysql-test/t/log_tables_debug.test:
  New test file. A debug feature is used to ensure that
  log entries are prefixed with a timestamp.
sql/log.cc:
  A debug feature is implemented to ensure that
  log entries are prefixed with a timestamp.

Re-enabled tests main.init_connect and rpl.rpl_init_slave.test for non-Windows
platforms.

Please remove this code upon fixing the bug.

WHERE and GROUP BY clause

Loose index scan may use range conditions on the argument of 
the MIN/MAX aggregate functions to find the beginning/end of 
the interval that satisfies the range conditions in a single go.
These range conditions may have open or closed minimum/maximum 
values. When the comparison returns 0 (equal) the code should 
check the type of the min/max values of the current interval 
and accept or reject the row based on whether the limit is 
open or not.
There was a wrong composite condition on checking this and it was
not working in all cases.
Fixed by simplifying the conditions and reversing the logic.

mysql-test/r/group_min_max.result:
  Bug #45386: test case
mysql-test/t/group_min_max.test:
  Bug #45386: test case
sql/opt_range.cc:
  Bug #45386: fix the check whether to use the value if on the
  interval boundry

This is the backmerge of 5.0.74sp1 into the main sources,
but effectively a null-merge, because the changes in that version
were backports of changes already present in later sources.