bzr push into mysql-trunk branch (venkata.sidagam:3799 to 3800)

[Venkata Sidagam]

 3800 Venkata Sidagam	2012-05-08 [merge]
      Null merge from mysql-5.5 to mysql-trunk

 3799 Jorgen Loland	2012-05-08
      Bug#13970015: ASSERT `MIN_ENDP || MAX_ENDP' FAILED IN 
                    HANDLER::MULTI_RANGE_READ_INFO_CONST
      
      When key_or() finds that two SEL_ARG trees form a full range
      (no upper or lower bound in the range; is always true), NULL 
      is returned. In most cases the range optimizer then forgets 
      about these trees, but when the trees belong to two different
      SEL_TREEs used in an index merge the always true range is only
      removed from one of the SEL_TREEs. 
      
      Index merge is a disjunct operation, meaning that the rows
      read from the different indexes shall be ORed. If the
      predicate for one of the indexes is always true then index 
      merge range access will effectively fetch all rows from the
      table. Range access in this case is not a good idea.

    modified:
      mysql-test/include/index_merge2.inc
      mysql-test/r/index_merge_myisam.result
      sql/opt_range.cc
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