selectivity function

I'm trying to include a sensitivity operator in a function. My issue is
that when I have my function, I get a call to SupportRequestSimplify, but
not SupportRequestSensitivity. It is not obvious what I am doing that is
incorrect.

My c (stub) function is:

PG_FUNCTION_INFO_V1(pgq3c_join_selectivity);
Datum pgq3c_join_selectivity(PG_FUNCTION_ARGS)
{
Node *rawreq = (Node *) PG_GETARG_POINTER(0);
Node *ret = NULL;

elog(WARNING,"in pgq3c_join_selectivity %d %d %d",
rawreq->type,T_SupportRequestSelectivity,T_SupportRequestSimplify);

if (IsA(rawreq, SupportRequestSelectivity))
{
elog(WARNING,"found SupportRequestSelectivity");
}
if (IsA(rawreq, SupportRequestSimplify))
{
elog(WARNING,"found SupportRequestSimplify");
}

PG_RETURN_POINTER(ret);
}

my sql function code is:

-- a selectivity function for the q3c join functionCREATE OR REPLACE
FUNCTION q3c_join_selectivity(internal)
RETURNS internal
AS 'MODULE_PATHNAME', 'pgq3c_join_selectivity'
LANGUAGE C IMMUTABLE STRICT ;

and my function definition is:

CREATE OR REPLACE FUNCTION q3c_join(leftra double precision,
leftdec double precision,
rightra double precision, rightdec double precision,
radius double precision)
RETURNS boolean AS'
SELECT (((q3c_ang2ipix($3,$4)>=(q3c_nearby_it($1,$2,$5,0))) AND
(q3c_ang2ipix($3,$4)<=(q3c_nearby_it($1,$2,$5,1))))
OR ((q3c_ang2ipix($3,$4)>=(q3c_nearby_it($1,$2,$5,2))) AND
(q3c_ang2ipix($3,$4)<=(q3c_nearby_it($1,$2,$5,3))))
OR ((q3c_ang2ipix($3,$4)>=(q3c_nearby_it($1,$2,$5,4))) AND
(q3c_ang2ipix($3,$4)<=(q3c_nearby_it($1,$2,$5,5))))
OR ((q3c_ang2ipix($3,$4)>=(q3c_nearby_it($1,$2,$5,6))) AND
(q3c_ang2ipix($3,$4)<=(q3c_nearby_it($1,$2,$5,7)))))
AND q3c_sindist($1,$2,$3,$4)<POW(SIN(RADIANS($5)/2),2)
AND ($5::double precision ==<<>>== ($1,$2,$3,$4)::q3c_type)
' LANGUAGE SQL IMMUTABLE COST 10 SUPPORT q3c_join_selectivity;

When I run my function, I get:

(base) [greg(dot)hennessy(at)localhost ~]$ psql q3c_test
Timing is on.
Output format is unaligned.
psql (13.4)
Type "help" for help.

q3c_test=# select count(*) from test as a, test1 as b where
q3c_join(a.ra,a.dec,b.ra,b.dec,.01);
WARNING: in pgq3c_join_selectivity 417 418 417
WARNING: found SupportRequestSimplify
count153
(1 row)Time: 9701.717 ms (00:09.702)
q3c_test=#

So, I see a call where I am asked for a SupportRequestSimplify, but not a
SupportRequestSelectivity.

I admit to not being an expert in postgres internals hacking. Is there
something obvious I am doing incorrect? How do I ensure my support Function
is asked for a SupportRequestSelectivity?