As reported in BUG #7715 , hstore's use of ? as an operator conflicts with JDBC's bind variables.
I think we could just alias ? to ~ and tell JDBC users to use that instead. 
 http://www.postgresql.org/message-id/E1TeIju-0003qb-WD@wrigleys.postgresql.org https://gist.github.com/seamusabshere/4715959/revisions
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