Thread: pgsql: Improve sorting speed by pre-extracting the first sort-key column

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)