OceanBase TABLE SCAN

obclient>CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT, c3 INT, c4 INT, 
      INDEX k1(c2,c3));
Query OK, 0 rows affected (0.09 sec)

Q1：
obclient>EXPLAIN EXTENDED SELECT * FROM t1 WHERE c1 = 1\G;
*************************** 1. row ***************************
Query Plan: 
| ==================================
|ID|OPERATOR |NAME|EST. ROWS|COST|
----------------------------------
|0 |TABLE GET|t1  |1        |53  |
==================================
Outputs & filters:
-------------------------------------
  0 - output([t1.c1(0x7f22fbe69340)], [t1.c2(0x7f22fbe695c0)], [t1.c3(0x7f22fbe69840)], [t1.c4(0x7f22fbe69ac0)]), filter(nil),
      access([t1.c1(0x7f22fbe69340)], [t1.c2(0x7f22fbe695c0)], [t1.c3(0x7f22fbe69840)], [t1.c4(0x7f22fbe69ac0)]), partitions(p0),
      is_index_back=false,
      range_key([t1.c1(0x7f22fbe69340)]), range[1 ; 1],
      range_cond([t1.c1(0x7f22fbe69340) = 1(0x7f22fbe68cf0)])

Q2：
obclient>EXPLAIN EXTENDED SELECT * FROM t1 WHERE c2 < 1 AND c3 < 1 AND
         c4 < 1\G;
*************************** 1. row ***************************
Query Plan: 
| ======================================
|ID|OPERATOR  |NAME  |EST. ROWS|COST |
--------------------------------------
|0 |TABLE SCAN|t1(k1)|100      |12422|
======================================

Outputs & filters:
-------------------------------------
  0 - output([t1.c1(0x7f22fbd1e220)], [t1.c2(0x7f227decec40)], [t1.c3(0x7f227decf9b0)], [t1.c4(0x7f22fbd1dfa0)]), filter([t1.c3(0x7f227decf9b0) < 1(0x7f227decf360)], [t1.c4(0x7f22fbd1dfa0) < 1(0x7f22fbd1d950)]),
      access([t1.c2(0x7f227decec40)], [t1.c3(0x7f227decf9b0)], [t1.c4(0x7f22fbd1dfa0)], [t1.c1(0x7f22fbd1e220)]), partitions(p0),
      is_index_back=true, filter_before_indexback[true,false],
      range_key([t1.c2(0x7f227decec40)], [t1.c3(0x7f227decf9b0)], [t1.c1(0x7f22fbd1e220)]), 
      range(NULL,MAX,MAX ; 1,MIN,MIN),
      range_cond([t1.c2(0x7f227decec40) < 1(0x7f227dece5f0)])