*** pgsql/src/backend/optimizer/README	2007/10/26 18:10:50	1.41
--- pgsql/src/backend/optimizer/README	2009/09/29 01:21:02	1.41.2.1
*************** operator is mergejoinable, so there is n
*** 467,473 ****
  get into EquivalenceClasses otherwise.  Aggregates are disallowed in WHERE
  altogether, so will never be found in a mergejoinable clause.)  This is just
  a convenience to maintain a uniform PathKey representation: such an
! EquivalenceClass will never be merged with any other.
  
  An EquivalenceClass also contains a list of btree opfamily OIDs, which
  determines what the equalities it represents actually "mean".  All the
--- 467,476 ----
  get into EquivalenceClasses otherwise.  Aggregates are disallowed in WHERE
  altogether, so will never be found in a mergejoinable clause.)  This is just
  a convenience to maintain a uniform PathKey representation: such an
! EquivalenceClass will never be merged with any other.  Note in particular
! that a single-item EquivalenceClass {a.x} is *not* meant to imply an
! assertion that a.x = a.x; the practical effect of this is that a.x could
! be NULL.
  
  An EquivalenceClass also contains a list of btree opfamily OIDs, which
  determines what the equalities it represents actually "mean".  All the