bizgres - bizgres: Improve sorting speed by pre-extracting the first

Log Message:
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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.

Simon Riggs, Tom Lane

Modified Files:
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    bizgres/postgresql/src/backend/executor:
        nodeSort.c (r1.1.1.2.2.1 -> r1.2)

(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/bizgres/bizgres/postgresql/src/backend/executor/nodeSort.c.diff?r1=1.1.1.2.2.1&r2=1.2)