const tables. This resulted in choosing extremely inefficient
execution plans in same cases when distribution of data in
joined were skewed (see the customer test case for the bug).



mysql-test/r/select.result:
  Added a test case for bug #21390: wrong estimate of rows
  after elimination of const tables.
  Includded a test case that checks the code added by the patch
  that handles outer joins with no matches after substitution of
  a const table in an efficient way.
mysql-test/t/select.test:
  Added a test case for bug #21390: wrong estimate of rows
  after elimination of const tables.
  Included a test case that checks the code added by the patch
  that handles outer joins with no matches after substitution of
  a const table in an efficient way.
sql/sql_select.cc:
  Fixed bug #21390: wrong estimate of rows after elimination of
  const tables. This resulted in choosing extremely inefficient
  execution plans in same cases when distribution of data in
  joined were skewed (see the customer test case for the bug).
  Also added the code to handle outer joins with no matches after
  substitution of a const table in an efficient way. 
  Corrected calculation of the null rejecting key conditions.