Backport from 5.1.
Raised STACK_MIN_SIZE for Debian GNU/Linux Sid,
Linux kernel 2.6.16,
gcc version 3.3.6 (Debian 1:3.3.6-13),
libc6-dbg 2.3.6.ds1-4,
Pentium4 (x86),
BUILD/compile-pentium-debug-max
Raised about 100 Bytes above the required minimum.

into  chilla.local:/home/mydev/mysql-5.0-merge

into  chilla.local:/home/mydev/mysql-5.0-merge

into  chilla.local:/home/mydev/mysql-4.1-merge

into  mysql.com:/data0/bk/mysql-5.0-kt

into  chilla.local:/home/mydev/mysql-4.1-bug12240

into  chilla.local:/home/mydev/mysql-5.0-bug12240

into  chilla.local:/home/mydev/mysql-5.0-bug12240

into  chilla.local:/home/mydev/mysql-4.1-bug12240

into  moonlight.intranet:/home/tomash/src/mysql_ab/mysql-4.1-bug9678

into  moonlight.intranet:/home/tomash/src/mysql_ab/mysql-5.0-real

into  moonlight.intranet:/home/tomash/src/mysql_ab/mysql-4.1-bug9678

into  mysql.com:/home/hf/mysql-5.0.mrg

into  chilla.local:/home/mydev/mysql-4.1-bug8283-one

into  chilla.local:/home/mydev/mysql-5.0-bug8283

Examined rows are counted for every join part. The per-join-part
counter was incremented over all iterations. The result variable
was replaced at the end of every iteration. The final result was
the number of examined rows by the join part that ended its
execution as the last one. The numbers of other join parts was
lost.

Now we reset the per-join-part counter before every iteration and
add it to the result variable at the end of the iteration. That
way we get the sum of all iterations of all join parts.

No test case. Testing this needs a look into the slow query log.
I don't know of a way to do this portably with the test suite.

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

into  neptunus.(none):/home/msvensson/mysql/mysql-4.1

into  mysql.com:/home/bk/MERGE/mysql-5.0-merge

into  mysql.com:/home/bk/MERGE/mysql-4.1-merge

into  trift2.:/MySQL/M50/push-5.0

After merge fix. MyISAM version 10.

into  chilla.local:/home/mydev/mysql-5.0-bug8283

into  chilla.local:/home/mydev/mysql-4.1-bug8283-one

OPTIMIZE TABLE with myisam_repair_threads > 1 performs a non-quick 
parallel repair. This means that it does not only rebuild all 
indexes, but also the data file.

Non-quick parallel repair works so that there is one thread per 
index. The first of the threads rebuilds also the new data file.

The problem was that all threads shared the read io cache on the
old data file. If there were holes (deleted records) in the table,
the first thread skipped them, writing only contiguous, non-deleted
records to the new data file. Then it built the new index so that
its entries pointed to the correct record positions. But the other
threads didn't know the new record positions, but put the positions
from the old data file into the index.

The new design is so that there is a shared io cache which is filled
by the first thread (the data file writer) with the new contiguous
records and read by the other threads. Now they know the new record
positions.

Another problem was that for the parallel repair of compressed
tables a common bit_buff and rec_buff was used. I changed it so
that thread specific buffers are used for parallel repair.

A similar problem existed for checksum calculation. I made this
multi-thread safe too.

into  mysql.com:/home/svoj/devel/mysql/engines/mysql-5.0-engines

into  may.pils.ru:/home/svoj/devel/bk/mysql-5.0-engines

into  may.pils.ru:/home/svoj/devel/bk/mysql-4.1-engines

into  mysql.com:/home/svoj/devel/mysql/BUG22937/mysql-5.0-engines

into  mysql.com:/home/svoj/devel/mysql/BUG22937/mysql-4.1-engines

This is addition to fix for bug21617. Valgrind reports an error when
opening merge table that has underlying tables with less indexes than
in a merge table itself.

Copy at most min(file->keys, table->key_parts) elements from rec_per_key array.
This fixes problems when merge table and subtables have different number of keys.

into  mysql.com:/home/svoj/devel/mysql/BUG21381/mysql-5.0-engines

into  mysql.com:/home/svoj/devel/mysql/BUG10974/mysql-5.0-engines

into  mysql.com:/home/svoj/devel/mysql/BUG21381/mysql-5.0-engines

into  mysql.com:/home/svoj/devel/mysql/BUG21381/mysql-4.1-engines

Though this is not storage engine specific problem, I was able to
repeat this problem with BDB and NDB engines only. That was the
reason to add a test case into ndb_update.test. As a result
different bad things could happen.

BDB has removed duplicate rows which is not expected.
NDB returns an error.

For multi table update notify storage engine about UPDATE IGNORE
as it is done in single table UPDATE.