Hi,
Craig just mentioned in an internal chat that there's no btree or even
hash opclass for the new pg_lsn type. That restricts what you can do
with it quite severely.
Imo this should be fixed for 9.4 - after all it was possible unto now to
index a table with lsns returned by system functions or have queries
with grouping on them without casting.
Greetings,
Andres Freund
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Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services