Must a C state transition function use palloc on the returned value?

Dirk Lutzebaeck <lutzeb@aeccom.com> writes:

I'm defining a new aggregate using a C transition function. It is of
type TEXT, so the C function gets pointers (*text) to the internal-state1 and
next-data-item parameters.

Question is if the returning value of type *text must be palloc'ed or
can be just taken from the input parameters.

The result must be a fresh palloc, since both inputs will be pfreed the
moment you return. 7.1 will copy the result for you if you are so
incautious as to try to return an input, but 7.0.* just falls over :-(

regards, tom lane

Tom Lane writes:

Dirk Lutzebaeck <lutzeb@aeccom.com> writes:

I'm defining a new aggregate using a C transition function. It is of
type TEXT, so the C function gets pointers (*text) to the internal-state1 and
next-data-item parameters.

Question is if the returning value of type *text must be palloc'ed or
can be just taken from the input parameters.

The result must be a fresh palloc, since both inputs will be pfreed the
moment you return. 7.1 will copy the result for you if you are so
incautious as to try to return an input, but 7.0.* just falls over :-(

Thanks! It works now...

Dirk