2011/5/11 Joseph Adams <joeyadams3.14...@gmail.com>: > On Tue, May 10, 2011 at 10:29 PM, Joseph Adams > <joeyadams3.14...@gmail.com> wrote: >> The VARIANT type, or similar, would be useful for the JSON data type >> I've been intermittently working on, as it would allow us to create a >> function like this: >> >> from_json(JSON) returns VARIANT > > This occurred to me: if PostgreSQL functions could return ANYELEMENT, > then we could just say: > > from_json(JSON) returns ANYELEMENT -- no intermediate VARIANT value > > Likewise, the variant conversion functions (which could be invoked > automatically) could be done this way: > > to_variant(ANYELEMENT) returns VARIANT > from_variant(VARIANT) returns ANYELEMENT > > However, I'm not familiar enough with the innards of PostgreSQL's type > system to know if returning ANYELEMENT would be possible and make > sense. >
it isn't possible. You can have a ANYELEMENT on input and output, or ANYELEMENT on input, but you ca't have ANYELEMENT just on output. The analogy for ANYELEMENT is C++ template. Regards Pavel Stehule VARIANT is maybe good idea - it can simplify a PL/pgSQL code - but though anybody about using this type in planner? > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
