Log Message:
-----------
Improve sorting speed by pre-extracting the first sort-key column of
each tuple, as per my proposal of several days ago. Also, clean up
sort memory management by keeping all working data in a separate memory
context, and refine the handling of low-memory conditions.
Modified Files:
--------------
pgsql/src/backend/executor:
nodeSort.c (r1.52 -> r1.53)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeSort.c.diff?r1=1.52&r2=1.53)
pgsql/src/backend/utils/sort:
tuplesort.c (r1.59 -> r1.60)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/sort/tuplesort.c.diff?r1=1.59&r2=1.60)