This performance degradation was due to the fact that some
cost evaluation code added into 4.1 in the function find_best was
not merged into the code of the function best_access_path added
together with other code for greedy optimizer.
Added a parameter to the function print_plan. The parameter contains
accumulated cost for a given partial join.
 
The patch does not include a special test case since this performance
degradation is hard to reproduse with a simple example.

TODO: make the function find_best use the function best_access_path
in order to remove duplication of code which might result in incomplete
merges in the future.

  Make InnoDB option "loose", as the server might be
  started with this option just to find out the test
  is to be skipped in the configuration (bug#17359)

into  rurik.mysql.com:/home/igor/mysql-5.0

into  poseidon.ndb.mysql.com:/home/tomas/mysql-5.0

into  poseidon.ndb.mysql.com:/home/tomas/mysql-5.0

into  mysql.com:/usr/local/home/marty/MySQL/mysql-5.0

into  neptunus.(none):/home/msvensson/mysql/my50-bug19190

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  rurik.mysql.com:/home/igor/dev/mysql-4.1-0

The bug caused wrong result sets for union constructs of the form
(SELECT ... ORDER BY order_list1 [LIMIT n]) ORDER BY order_list2.
For such queries order lists were concatenated and limit clause was
completely neglected. 

Fixes for Bug#12429: Replication tests fail: "Slave_IO_Running" (?) differs related to MySQL 4.1
and Bug#16920 rpl_deadlock_innodb fails in show slave status (reported for MySQL 5.1)

into  three.local.lan:/home/matthias/Arbeit/mysql-5.0/src-1

into  mysql.com:/usr/local/home/marty/MySQL/mysql-5.0

into  three.local.lan:/home/matthias/Arbeit/mysql-5.0/src-1

  Remove duplicate test case for bug#14169

into  production.mysql.com:/usersnfs/mleich/src

  Clean up test case for bug#14169

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

Temporarily commented out a query from the test case for bug 14169 to make it pass with --ps-protocol.

into  rurik.mysql.com:/home/igor/dev/mysql-4.1-2

into  mysql.com:/home/jimw/my/mysql-5.0-clean

into moonbone.local:/work/14169-bug-4.1-mysql

  Corrected test case for the bug#14169 to make it pass in --ps-protocol mode.

After a locking error the open table(s) were not fully
cleaned up for reuse. But they were put into the open table
cache even before the lock was tried. The next statement
reused the table(s) with a wrong lock type set up. This
tricked MyISAM into believing that it don't need to update
the table statistics. Hence CHECK TABLE reported a mismatch
of record count and table size.

Fortunately nothing worse has been detected yet. The effect
of the test case was that the insert worked on a read locked
table. (!)

I added a new function that clears the lock type from all
tables that were prepared for a lock. I call this function
when a lock failes.

No test case. One test would add 50 seconds to the
test suite. Another test requires file mode modifications.
I added a test script to the bug report. It contains three
cases for failing locks. All could reproduce a table
corruption. All are fixed by this patch.

This bug was not lock timeout specific.

into  mysql.com:/home/stewart/Documents/MySQL/5.0/merge

The bug caused a reported index corruption in the cases when
key_cache_block_size was not a multiple of myisam_block_size,
e.g. when key_cache_block_size=1536 while myisam_block_size=1024.

into  mysql.com:/home/matthias/Arbeit/mysql-4.1/src-1

into  mysql.com:/home/matthias/Arbeit/mysql-5.0/src-1

  Stepped up version to 5.0.20a

into  neptunus.(none):/home/msvensson/mysql/mysql-5.0-release

 - Apply patch to remove dependency on C++ libs when linking "libmysql" from c

  revert bug#16855 "fix" per Monty's request