Update wording in optimizer/README for EquivalenceClasses

d69d45a5a changed how em_is_child members are stored in
EquivalenceClasses.  Children are no longer stored in the ec_members
list.  optimizer/README mentioned that most operations "should ignore
child members", but that felt a little untrue now since child members
are now stored in a separate place, they simply won't be found by the
normal means of looking (a foreach loop over ec_members), and if you don't
find them, there's technically no need to "ignore" them.

Here we tweak the wording slightly to reflect the new storage location
for child members.

Reported-by: Amit Langote <[email protected]>
Author: Amit Langote <[email protected]>
Author: David Rowley <[email protected]>
Discussion: https://postgr.es/m/CA+HiwqE8v=EuAP_3F_A2xn8zWx+nG_etW_Fe_DvKO-Fkx=+DdQ@mail.gmail.com

diff --git a/src/backend/optimizer/README b/src/backend/optimizer/README
index 21c2db5a85c9e4739ac13d0924fed1cd7582002f..9c724ccfabf831ba813b8fe33fe8909190d8dc92 100644 (file)
--- a/src/backend/optimizer/README
+++ b/src/backend/optimizer/README
@@ -902,7 +902,7 @@ contain the equivalent child-relation variables or expressions.  These
 members are *not* full-fledged members of the EquivalenceClass and do not
 affect the class's overall properties at all.  They are kept only to
 simplify matching of child-relation expressions to EquivalenceClasses.
-Most operations on EquivalenceClasses should ignore child members.
+Most operations on EquivalenceClasses needn't look at child members.
 
 
 PathKeys