analyze too slowly with 100k partition

[hawkingrei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create many tables like this, then analyze it.

 CREATE TABLE `sbtest1` (                                                         
   `id` int NOT NULL AUTO_INCREMENT,                                              
   `k` int NOT NULL DEFAULT '0',                                                  
   `c` char(120) NOT NULL DEFAULT '',                                             
   `pad` char(60) NOT NULL DEFAULT '',                                            
   `ec1` varchar(40) DEFAULT NULL,                                                
   `ec2` varchar(40) DEFAULT NULL,                                                
   `ec3` varchar(40) DEFAULT NULL,                                                
   `ec4` varchar(40) DEFAULT NULL,                                                
   `ec5` varchar(40) DEFAULT NULL,                                                
   `ec6` varchar(40) DEFAULT NULL,                                                
   `ec7` varchar(40) DEFAULT NULL,                                                
   `ec8` varchar(40) DEFAULT NULL,                                                
   `ec9` varchar(40) DEFAULT NULL,                                                
   `ec10` varchar(40) DEFAULT NULL,                                               
   PRIMARY KEY (`id`) /*T![clustered_index] CLUSTERED */,                         
   KEY `k_1` (`k`),                                                               
   KEY `ek1` (`ec1`(30)),                                                         
   KEY `ek2` (`ec2`(30)),                                                         
   KEY `ek3` (`ec3`(30)),                                                         
   KEY `ek4` (`ec4`(30))                                                          
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin AUTO_INCREMENT=30001 
 PARTITION BY RANGE (`id`)                                                        
 (PARTITION `p1` VALUES LESS THAN (1001),                                         
  PARTITION `p2` VALUES LESS THAN (2001),                                         
  PARTITION `p3` VALUES LESS THAN (3001),                                         
  PARTITION `p4` VALUES LESS THAN (4001),                                         
  PARTITION `p5` VALUES LESS THAN (5001),                                         
  PARTITION `p6` VALUES LESS THAN (6001),                                         
  PARTITION `p7` VALUES LESS THAN (7001),                                         
  PARTITION `p8` VALUES LESS THAN (8001),                                         
  PARTITION `p9` VALUES LESS THAN (9001),                                         
  PARTITION `p10` VALUES LESS THAN (MAXVALUE))                                    

2. What did you expect to see? (Required)

it should be quick.

3. What did you see instead (Required)

but it is very slow.

4. What is your TiDB version? (Required)