pgsql: Fix oversight in handling of row-comparison index keys: if the

Log Message:
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Fix oversight in handling of row-comparison index keys: if the row comparison
doesn't exactly match the index, we may have to change our initial positioning
strategy. For example, given an index on (f1,f2,f3) and a WHERE condition
"ROW(f1,f3) > ROW(2,3)", the code extracted the initial-positioning condition
"f1 > 2", which is wrong ... it has to be "f1 >= 2", else some rows matching
the WHERE condition may fail to be returned.

Applying patch to 8.2 only --- I'll fix it in HEAD later as part of the
planned index improvements (reverse-sort and NULLS FIRST/LAST work).

Tags:
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REL8_2_STABLE

Modified Files:
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pgsql/src/backend/access/nbtree:
nbtsearch.c (r1.107 -> r1.107.2.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtsearch.c.diff?r1=1.107&r2=1.107.2.1)