MySQL挂在一个大表中，现在需要很长时间才能连接

MySql接受连接的速度很慢，在试图删除一个包含5000万条记录的大表的尝试失败后，MySql变得迟钝。过去是即时连接，现在只需20-30秒即可连接

运行mysqlcheck会在表中显示正确的结果，但是，显示引擎INNODB状态看起来不正确：

它从以下几行开始：

+----+---+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

这将持续许多行，然后：

----------------------------------------------+
| InnoDB |      |
=====================================
2017-01-31 19:03:05 0x7f2be82e5700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 35 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 19 srv_active, 0 srv_shutdown, 1234 srv_idle
srv_master_thread log flush and writes: 1253
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 91
OS WAIT ARRAY INFO: signal count 74
RW-shared spins 0, rounds 58, OS waits 23
RW-excl spins 0, rounds 205, OS waits 0
RW-sx spins 0, rounds 0, OS waits 0
Spin rounds per wait: 58.00 RW-shared, 205.00 RW-excl, 0.00 RW-sx
------------
TRANSACTIONS
------------
Trx id counter 40192594
Purge done for trx's n:o < 40190602 undo n:o < 0 state: running but idle
History list length 2280
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421306474252112, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
 ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 0
369979 OS file reads, 61 OS file writes, 15 OS fsyncs
286.85 reads/s, 16384 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 2193, seg size 2195, 0 merges
merged operations:
 insert 0, delete mark 0, delete 0
discarded operations:
 insert 0, delete mark 0, delete 0
Hash table size 1182691, node heap has 0 buffer(s)
Hash table size 1182691, node heap has 3 buffer(s)
Hash table size 1182691, node heap has 3 buffer(s)
Hash table size 1182691, node heap has 6 buffer(s)
Hash table size 1182691, node heap has 2 buffer(s)
Hash table size 1182691, node heap has 2 buffer(s)
Hash table size 1182691, node heap has 1 buffer(s)
Hash table size 1182691, node heap has 0 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 310536690314
Log flushed up to   310536690314
Pages flushed up to 310536690314
Last checkpoint at  310536690305
0 pending log flushes, 0 pending chkp writes
16 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 4397727744
Dictionary memory allocated 39828543
Buffer pool size   262112
Free buffers       0
Database pages     262095
Old database pages 96806
Modified db pages  0
Pending reads      1
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 103, not young 6145557
0.00 youngs/s, 92166.80 non-youngs/s
Pages read 369591, created 34, written 37
286.88 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 368 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 262095, unzip_LRU len: 0
I/O sum[120336]:cur[304], unzip sum[0]:cur[0]
----------------------
INDIVIDUAL BUFFER POOL INFO
----------------------
---BUFFER POOL 0
Buffer pool size   32764
Free buffers       0
Database pages     32761
Old database pages 12102
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 12, not young 782981
0.00 youngs/s, 12008.66 non-youngs/s
Pages read 46266, created 0, written 3
36.46 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 369 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32761, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 1
Buffer pool size   32764
Free buffers       0
Database pages     32760
Old database pages 12090
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 23, not young 714985
0.00 youngs/s, 10882.83 non-youngs/s
Pages read 43701, created 0, written 0
33.54 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 361 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32760, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 2
Buffer pool size   32764
Free buffers       0
Database pages     32762
Old database pages 12102
Modified db pages  0
Pending reads      1
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 12, not young 826273
0.00 youngs/s, 12544.36 non-youngs/s
Pages read 47653, created 0, written 0
40.11 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 363 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32762, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 3
Buffer pool size   32764
Free buffers       0
Database pages     32763
Old database pages 12103
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 11, not young 789399
0.00 youngs/s, 10819.38 non-youngs/s
Pages read 46867, created 0, written 0
34.46 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 364 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32763, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 4
Buffer pool size   32764
Free buffers       0
Database pages     32762
Old database pages 12089
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 24, not young 716775
0.00 youngs/s, 10601.24 non-youngs/s
Pages read 45316, created 0, written 0
32.43 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 371 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32762, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 5
Buffer pool size   32764
Free buffers       0
Database pages     32762
Old database pages 12094
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 20, not young 816196
0.00 youngs/s, 12974.26 non-youngs/s
Pages read 47369, created 0, written 0
39.77 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 378 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32762, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 6
Buffer pool size   32764
Free buffers       0
Database pages     32764
Old database pages 12113
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 1, not young 739215
0.00 youngs/s, 11328.79 non-youngs/s
Pages read 46339, created 34, written 34
34.51 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 373 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32764, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
---BUFFER POOL 7
Buffer pool size   32764
Free buffers       0
Database pages     32761
Old database pages 12113
Modified db pages  0
Pending reads      0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 0, not young 759733
0.00 youngs/s, 11007.29 non-youngs/s
Pages read 46080, created 0, written 0
35.60 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 999 / 1000, young-making rate 0 / 1000 not 367 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 32761, unzip_LRU len: 0
I/O sum[15042]:cur[38], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
1 read views open inside InnoDB
Process ID=2785, Main thread ID=139826948695808, state: sleeping
Number of rows inserted 0, updated 0, deleted 0, read 14
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================
+--------+------+---------------------------------------------------------------
                                                                                           --------------------------------------------------------------------------------                                                                                                --------------------------------------------------------------------------------                                                                                                --------------------------------------------------------------------------------                                                                                                -------------------------------------------------------------------------------- 

最后，输出在开始时以多行破折号和加号结束

---

请告知我故障排除和维修的其他步骤。

如果您怀疑innoDB出现异常行为，您可以查看引擎正在执行的操作，这非常昂贵，因此在正常情况下不要执行此操作。手册说明如下：

启用InnoDB监视器以获取有关问题的信息，请参阅 第14.17节，“InnoDB监视器”。如果问题是 与性能相关，或者您的服务器似乎挂起，您应该 启用标准监视器打印有关内部监视器的信息 InnoDB的状态。如果问题出在锁上，请启用锁 班长如果问题在于创建表或其他数据 字典操作，使表监视器能够打印内容 InnoDB内部数据字典的。查看表空间信息的步骤 启用表空间监视器

InnoDB临时在下启用标准InnoDB监视器输出 以下情况：

长时间的信号灯等待

InnoDB在缓冲池中找不到可用块

超过67%的缓冲池被锁堆或自适应哈希索引占用

---

看来，问题和大表掉落问题的巧合并不是原因。这是网络上的DNS问题

将跳过名称解析添加到/etc/my.cnf（我的系统是CentOS）并重新启动服务器后，连接似乎恢复正常

[mysqld]
skip-name-resolve

---

如果您中止了在事务中删除大型表的尝试，则在中止时该表处于脏状态。MySQL正在重建那个大表，以便它与事务开始前的状态相匹配。对于这一点，您真的无能为力，它是通过设计来恢复该表的，但恢复该状态并不一定容易。谢谢。有没有办法让我看到数据库正在恢复，它确实在重建？