Added a q3c_sindist_bool function to allow for calculating a better Selectivity

[gshennessy]

Have a selectivity function for q3c_sindist_bool.

[segasai]

I looked at the patch, but I actually forgot that I already have selectivity on for the q3c_join() so nothing is needed there. It is done through the weird operator

q3c/scripts/q3c--2.0.0.sql

Line 209 in 040de14

AND ($5::double precision ==<<>>== ($1,$2,$3,$4)::q3c_type)

with this selectivity function

q3c/q3c.c

Line 94 in 040de14

Datum pgq3c_sel(PG_FUNCTION_ARGS)

In fact

explain select * from gaia_dr3.gaia_source as g, gaia_dr3.gaia_source as g1 where q3c_join(g.ra,g.dec,g1.ra,g1.dec,5./3600);

estimates the number of rows to be 60 millions which is pretty sensible (given it asssumes independent positions).

So I don't think q3c_join can be improved with your patch. What I can do is to do the same thing for q3c_radial_query() which currently doesnt' have the selectivity implemented

[gshennessy]

I need to do more A/B testing, if only for my own understanding.