A little fun with InnoDB multi-versioning（14.有关InnoDB多版本中的一个小问题）

ysql> show create table t G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `a` int(10) unsigned NOT NULL,
  `b` int(10) unsigned NOT NULL,
  PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> select * from t;
Empty set (5.20 sec)

mysql> select count(*) from t;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (5.22 sec)

mysql> select * from t where a = 10;
Empty set (0.00 sec)

mysql> select * from t where a < 10;
Empty set (5.35 sec)

mysql> select * from t where a > 10;
Empty set (5.41 sec)

mysql> select * from t where a in (10, 20, 30);
Empty set (0.00 sec)

mysql> select * from t where a > 1000000;
Empty set (0.00 sec)

mysql> select * from t where a > 500000;
Empty set (2.60 sec)

mysql> show processlist;
+----+------+-----------------+------+---------+------+-------+------------------+
| Id | User | Host            | db   | Command | Time | State | Info             |
+----+------+-----------------+------+---------+------+-------+------------------+
|  6 | root | localhost:34840 | test | Query   |    0 | init  | show processlist |
|  8 | root | localhost:34842 | test | Sleep   | 2116 |       | NULL             |
+----+------+-----------------+------+---------+------+-------+------------------+
2 rows in set (0.00 sec)

---TRANSACTION 1481, ACTIVE 2183 sec
3487 lock struct(s), heap size 570920, 2001743 row lock(s), undo log entries 11000000
MySQL thread id 8, OS thread handle 0x7fca27ba2700, query id 5000144 localhost 127.0.0.1 root cleaning up 

mysql> select * from information_schema.innodb_trx G
*************************** 1. row ***************************
                    trx_id: 1481
                 trx_state: RUNNING
               trx_started: 2014-04-17 01:38:27
     trx_requested_lock_id: NULL
          trx_wait_started: NULL
                trx_weight: 11003487
       trx_mysql_thread_id: 8
                 trx_query: NULL
       trx_operation_state: NULL
         trx_tables_in_use: 0
         trx_tables_locked: 0
          trx_lock_structs: 3487
     trx_lock_memory_bytes: 570920
           trx_rows_locked: 2001743
         trx_rows_modified: 11000000
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
 trx_adaptive_hash_latched: 0
 trx_adaptive_hash_timeout: 10000
          trx_is_read_only: 0
trx_autocommit_non_locking: 0
1 row in set (0.01 sec)

#!/usr/bin/env ruby

require "mysql"

m = Mysql.new("127.0.0.1", "root", "", "test", 13000)

m.query("DROP TABLE IF EXISTS t")
m.query("CREATE TABLE t (a INT UNSIGNED NOT NULL, b INT UNSIGNED NOT NULL, PRIMARY KEY (a)) ENGINE=InnoDB")

m.query("START TRANSACTION")

(1..1000000).each do |i|
  m.query("INSERT INTO t (a, b) VALUES (#{i}, 0)")
  puts "Inserted #{i} rows..." if i % 10000 == 0
end

(1..10).each do |i|
  m.query("UPDATE t SET b=#{i}")
  puts "Updated #{i} times..."
end

sleep 1000000