pub unsafe fn histogram_selectivity(
arg_vardata: *mut VariableStatData,
arg_opproc: *mut FmgrInfo,
arg_collation: Oid,
arg_constval: Datum,
arg_varonleft: bool,
arg_min_hist_size: c_int,
arg_n_skip: c_int,
arg_hist_size: *mut c_int,
) -> f64