hstore ==> and deprecate =>

I believe that the consensus was mostly in favor of deprecating => as
an operator name, with the intent to abolish it completely in a future
release. Attached is a patch to implement ==> as an alternative
operator name for hstore, and to make the backend throw a warning when
=> is used as an operator name.

One wart is that => is used not only as a SQL-level operator, but also
by hstore_in() when interpreting hstore-type literals, and by
hstore_out() when generating them. My gut feeling is that we should
leave this part alone and only muck with the SQL operator, but perhaps
someone will care to argue the point.

http://archives.postgresql.org/pgsql-hackers/2010-05/msg01501.php

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company