gistfile1.txt

CREATE TABLE `sbtest1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `k` int(11) NOT NULL DEFAULT '0',
  `c` char(120) NOT NULL DEFAULT '',
  `pad` char(60) NOT NULL DEFAULT '',
  KEY `xid` (`id`),
  KEY `k_1` (`k`)
) ENGINE=InnoDB AUTO_INCREMENT=2000001 DEFAULT CHARSET=latin1;

bin/mysql test -e 'explain SELECT c
             FROM sbtest1
             WHERE id IN (1000001, 1000002, 1000003, 1000004, 1000005, 1000006, 1000007, 1000008, 1000009, 1000010,
             1000011, 1000012, 1000013, 1000014, 1000015, 1000016, 1000017, 1000018, 1000019, 1000020, 
             1000021, 1000022, 1000023, 1000024, 1000025, 1000026, 1000027, 1000028, 1000029, 1000030,
             1000031, 1000032, 1000033, 1000034, 1000035, 1000036, 1000037, 1000038, 1000039, 1000040,
             1000041, 1000042, 1000043, 1000044, 1000045, 1000046, 1000047, 1000048, 1000049, 1000050,
             1000051, 1000052, 1000053, 1000054, 1000055, 1000056, 1000057, 1000058, 1000059, 1000060,
             1000061, 1000062, 1000063, 1000064, 1000065, 1000066, 1000067, 1000068, 1000069, 1000070,
             1000071, 1000072, 1000073, 1000074, 1000075, 1000076, 1000077, 1000078, 1000079, 1000080,
             1000081, 1000082, 1000083, 1000084, 1000085, 1000086, 1000087, 1000088, 1000089, 1000090,
             1000091, 1000092, 1000093, 1000094, 1000095, 1000096, 1000097, 1000098, 1000099, 1000100)'

*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: sbtest1
   partitions: NULL
         type: range
possible_keys: xid
          key: xid
      key_len: 4
          ref: NULL
         rows: 100
     filtered: 100.00
        Extra: Using index condition

bin/mysql test -e 'show indexes from sbtest1\G'
mysql: [Warning] Using a password on the command line interface can be insecure.
*************************** 1. row ***************************
        Table: sbtest1
   Non_unique: 1
     Key_name: xid
 Seq_in_index: 1
  Column_name: id
    Collation: A
  Cardinality: 1921330
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Visible: YES