of MAXBACKENDS is now 1024, since all it's costing is about 32 bytes of memory
per array slot.  configure's --with-maxbackends switch now controls DEF_MAXBACKENDS
which is simply the default value of the postmaster's -N switch.  Thus,
the out-of-the-box configuration will still limit you to 64 backends,
but you can go up to 1024 backends simply by restarting the postmaster with
a different -N switch --- no rebuild required.

From: Michael Meskes <Michael_Meskes@topmail.de>

See Changes file...

calling PQsetdb ...

postmaster will release whatever it did get before dying.

(--with-maxbackends).  Add a postmaster switch (-N backends) that allows
the limit to be reduced at postmaster start time.  (You can't increase it,
sorry to say, because there are still some fixed-size arrays.)
Grab the number of semaphores indicated by min(MAXBACKENDS, -N) at
postmaster startup, so that this particular form of bogus configuration
is exposed immediately rather than under heavy load.

client connection.

symmetry with regprocout.

what is_opclause will accept.

A test case is:
create table linetab (x line);
select * from linetab where ?| x;
which coredumps in 6.4.2 and current sources.

 decade, century, or millenium.