null 查询结果不正确

CREATE TABLE "TBL_GRP_TSK_INFO" (
  "MODNO" VARCHAR2(15) NOT NULL,
  "TASKID" VARCHAR2(32),
  "BQTYPE" VARCHAR2(4),
  ......
  "PAY_STAT" VARCHAR2(1),
  ......
  CONSTRAINT "PK_TBL_GRP_TSK_INFO" PRIMARY KEY ("MODNO")
) COMPRESS FOR ARCHIVE REPLICA_NUM = 3 BLOCK_SIZE = 16384 USE_BLOOM_FILTER = FALSE TABLET_SIZE = 134217728 PCTFREE = 0;


CREATE INDEX "GPS"."IDX_TBL_GRP_TSK_INFO_06" on "GPS"."TBL_GRP_TSK_INFO" (
 "BQTYPE",
 "PAY_STAT"
) GLOBAL ;

select count(*) from (select 
  modno
from
  tbl_grp_tsk_info t
where
  (
    t.bqtype = 'PLZR' or (
      t.isapp = '1' and t.bqtype = 'BQZR'
    )
  ) and tasksta = '99' and pay_stat != 'S' and pay_stat != 'F' and isnewobj = '0' and trim(isQFB) is null and pay_stat != 'U' )

====================================================================
|ID|OPERATOR            |NAME                      |EST. ROWS|COST |
--------------------------------------------------------------------
|0 |EXCHANGE IN REMOTE  |                          |1        |12347|
|1 | EXCHANGE OUT REMOTE|                          |1        |12347|
|2 |  TABLE SCAN        |T(IDX_TBL_GRP_TSK_INFO_06)|1        |12347|
====================================================================

Outputs & filters: 
-------------------------------------
  0 - output([T.MODNO(0x7ee6fab04170)]), filter(nil)
  1 - output([T.MODNO(0x7ee6fab04170)]), filter(nil)
  2 - output([T.MODNO(0x7ee6fab04170)]), filter([T.ISNEWOBJ(0x7ee6fab01030) = '0'(0x7ee6fab00910)], [T.BQTYPE(0x7ee6faafb450) = 'PLZR'(0x7ee6faaf8c50) OR T.ISAPP(0x7ee6faafb740) = '1'(0x7ee6faaf9fb0) AND T.BQTYPE(0x7ee6faafb450) = 'BQZR'(0x7ee6faafac30)(0x7ee6faaf9330)(0x7ee6faaf7fd0)], [T.TASKSTA(0x7ee6faafe0b0) = '99'(0x7ee6faafd990)], [(T_OP_IS, trim(T.ISQFB(0x7ee6fab02c00))(0x7ee6fab01440), NULL, 0)(0x7ee6fab02210)]), 
      access([T.BQTYPE(0x7ee6faafb450)], [T.ISAPP(0x7ee6faafb740)], [T.TASKSTA(0x7ee6faafe0b0)], [T.ISNEWOBJ(0x7ee6fab01030)], [T.ISQFB(0x7ee6fab02c00)], [T.MODNO(0x7ee6fab04170)]), partitions(p0), 
      is_index_back=true, filter_before_indexback[false,false,false,false], 
      range_key([T.BQTYPE(0x7ee6faafb450)], [T.PAY_STAT(0x7ee6faaff180)], [T.MODNO(0x7ee6fab04170)]), range(PLZR,MIN,MIN ; PLZR,F,MIN), (PLZR,F,MAX ; PLZR,S,MIN), (PLZR,S,MAX ; PLZR,U,MIN), (PLZR,U,MAX ; PLZR,NULL,MIN), (BQZR,MIN,MIN ; BQZR,F,MIN), (BQZR,F,MAX ; BQZR,S,MIN), (BQZR,S,MAX ; BQZR,U,MIN), (BQZR,U,MAX ; BQZR,NULL,MIN), 
      range_cond([T.PAY_STAT(0x7ee6faaff180) != 'S'(0x7ee6faafea60)], [T.PAY_STAT(0x7ee6faaff180) != 'F'(0x7ee6faaffb30)], [T.PAY_STAT(0x7ee6faaff180) != 'U'(0x7ee6fab03630)])

Used Hint:
-------------------------------------
  /*+
      NO_REWRITE
  */

Outline Data:
-------------------------------------
  /*+
      BEGIN_OUTLINE_DATA
      INDEX(@"SEL$1" "GPS.T"@"SEL$1" "IDX_TBL_GRP_TSK_INFO_06")
      NO_REWRITE
      END_OUTLINE_DATA
  */

Plan Type:
-------------------------------------
REMOTE

Optimization Info:
-------------------------------------

T:table_rows:3696815, physical_range_rows:2048, logical_range_rows:1709, index_back_rows:1709, output_rows:0, est_method:local_storage, optimization_method=cost_based, avaiable_index_name[IDX_TBL_GRP_TSK_INFO_06,IDX_TBL_GRP_TSK_INFO_01,TBL_GRP_TSK_INFO], pruned_index_name[IDX_TBL_GRP_TSK_INFO_08,IDX_TBL_GRP_TSK_INFO_04,IDX_TBL_GRP_TSK_INFO_07,IDX_TBL_GRP_TSK_INFO_05,IDX_TBL_GRP_TSK_INFO_10,IDX_TBL_GRP_TSK_INFO_11,IDX_TBL_GRP_TSK_INFO_02,IDX_TBL_GRP_TSK_INFO_03], estimation info[table_id:1105009185973522, (table_type:1, version:0-1682532010457701-1682532010457701, logical_rc:1601, physical_rc:1601), (table_type:0, version:1682532000646043-1682532000646043-9223372036854775807, logical_rc:108, physical_rc:447)]
Parameters
-------------------------------------