Solr SQL doesn't support IS NULL / IS NOT NULL operators

SELECT dateAsInt, a_s, b_s FROM $ALIAS WHERE b_s IS NOT NULL

{a_s=hello48, b_s=foo, dateAsInt=20210218}
{a_s=hello47, b_s=null, dateAsInt=20210217}

7632 INFO  (qtp1443077678-315) [n:127.0.0.1:55346_solr c:coll2 s:shard1 r:core_node3 x:coll2_shard1_replica_n1 ] o.a.s.c.S.Request [coll2_shard1_replica_n1]  webapp=/solr path=/export params={q=*:*&distrib=false&indent=off&fl=dateAsInt,a_s,b_s,_version_&sort=_version_+desc&wt=json&version=2.2} hits=13 status=0 QTime=29