Doc: update libpq's documentation for PQfn().
Mention specifically that you can't call aggregates, window functions,
or procedures this way (the inability to call SRFs was already
mentioned).
Also, the claim that PQfn doesn't support NULL arguments or results
has been a lie since we invented protocol 3.0. Not sure why this
text was never updated for that, but do it now.
Discussion: https://postgr.es/m/2039442.1615317309@sss.pgh.pa.us
Branch
------
REL_13_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/7c810bd028a7be3ce32beb438db072bd02592869
Modified Files
--------------
doc/src/sgml/libpq.sgml | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)
