The function test_if_skip_sort_order ignored any covering index used for ref
access of a table in a query with ORDER BY if this index was incompatible 
with the ORDER BY list and there was another covering index compatible with
this list. 
As a result sub-optimal execution plans were chosen for some queries with
ORDER BY clause. 

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.1-rpl-merge

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.1-rpl-merge

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.1-rpl-merge

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.0-rpl-merge

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.1-rpl-merge

into  magare.gmz:/home/kgeorge/mysql/work/merge-build-5.1-bugteam

into  mats-laptop.(none):/home/bk/b29020-mysql-5.1-rpl

tables is not zero any more. For row-based logging, there is an extra commit
for sending rows changed by the statement to the binary log.

into  magare.gmz:/home/kgeorge/mysql/work/merge-build-5.1-bugteam

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.1-rpl-merge

into  dl145h.mysql.com:/data0/mkindahl/mysql-5.0-rpl-merge

into  magare.gmz:/home/kgeorge/mysql/work/merge-build-5.1-bugteam

into  magare.gmz:/home/kgeorge/mysql/work/merge-build-5.1-bugteam

into  amd64.(none):/src/bug26243/my51-bug26243

into  mysql1000.(none):/home/andrei/MySQL/MERGE/5.1-main2rpl

If a binlog file is manually replaced with a namesake directory the internal purging did
not handle the error of deleting the file so that eventually
a post-execution guards fires an assert.

Fixed with reusing a snippet of code for bug@18199 to tolerate lack of the file but no other error 
at an attempt to delete it.
The same applied to the index file deletion.

The cset carries pieces of manual merging.

into  macbook.gmz:/Users/kgeorge/mysql/work/pb-5.1-bugteam

into  macbook.gmz:/Users/kgeorge/mysql/work/pb-5.1-bugteam

into  mysql1000.(none):/home/andrei/MySQL/MERGE/5.1-main2rpl

into  mysql1000.(none):/home/andrei/MySQL/MERGE/5.1-main2rpl

into  macbook.gmz:/Users/kgeorge/mysql/work/pb-5.1-bugteam

into  amd64.(none):/src/bug26243/my51-bug26243

into  amd64.(none):/src/bug26243/my51-bug26243

into  quad.opbmk:/mnt/raid/alik/MySQL/devel/5.1-bt-merged

into  amd64.(none):/src/bug26243/my51-bug26243

into  amd64.(none):/src/bug26243/my50-bug26243

  1. Use 'dat' extension, because it is handled in Makefile.am;
  2. Fix typo: the bug id is 35469, not 35649.

into  amd64.(none):/src/bug26243/my50-bug26243