SQLite

        assert( j>=pLoop->u.btree.nEq 
            || (pLoop->aLTerm[j]==0)==(j<pLoop->nSkip)
        );
        if( j<pLoop->u.btree.nEq && j>=pLoop->nSkip ){
          u16 eOp = pLoop->aLTerm[j]->eOperator;

          /* Skip over == and IS and ISNULL terms.  (Also skip IN terms when
          ** doing WHERE_ORDERBY_LIMIT processing).  Except, IS and ISNULL
          ** terms imply that the index is not UNIQUE NOT NULL in which case
          ** the loop need to be marked as not order-distinct because it can
          ** have repeated NULL rows.
          **
          ** If the current term is a column of an ((?,?) IN (SELECT...)) 
          ** expression for which the SELECT returns more than one column,
          ** check that it is the only column used by this loop. Otherwise,
          ** if it is one of two or more, none of the columns can be
          ** considered to match an ORDER BY term.
          */
          if( (eOp & eqOpMask)!=0 ){
            if( eOp & (WO_ISNULL|WO_IS) ){
              testcase( eOp & WO_ISNULL );
              testcase( eOp & WO_IS );
              testcase( isOrderDistinct );
              isOrderDistinct = 0;
            }
            continue;  
          }else if( ALWAYS(eOp & WO_IN) ){
            /* ALWAYS() justification: eOp is an equality operator due to the
            ** j<pLoop->u.btree.nEq constraint above.  Any equality other

} {
  one 0 1
  one 1 1
  two 0 1
  two 1 1
}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 3000 {
  CREATE TABLE t0 (c0, c1 NOT NULL DEFAULT 1, c2, PRIMARY KEY (c0, c1));
  INSERT INTO t0(c2) VALUES (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL);
  INSERT INTO t0(c2) VALUES('a');
}

do_execsql_test 3010 {
  SELECT DISTINCT * FROM t0 WHERE NULL IS t0.c0;
} {
  {} 1 {}
  {} 1 a
}

do_execsql_test 3020 {
  ANALYZE;
}

do_execsql_test 3030 {
  SELECT DISTINCT * FROM t0 WHERE NULL IS c0;
} {
  {} 1 {}
  {} 1 a
}

finish_test