MySQL在创建表为SELECT时锁定

我正在运行以下（虚拟）查询

CREATE TABLE large_temp_table AS 
    SELECT a.*, b.*, c.* 
    FROM a
    LEFT JOIN b ON a.foo = b.foo
    LEFT JOIN c ON a.bar = c.bar

假设查询需要10分钟才能运行。在表a，b或c运行时尝试更新它的值将等待上面的查询首先完成。我想避免这种锁定（数据一致性不重要）。我该如何实现？

使用：MySQL 5.1.41和InnoDB表

ps SET事务隔离级别读取未提交；行为无变化

更新 在执行查询时，SHOW ENGINE INNODB STATUS的输出如下（我在这里故意进行了非常慢的查询）

=====================================
120323 15:26:29 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 8 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 1470, signal count 1468
Mutex spin waits 0, rounds 7525, OS waits 112
RW-shared spins 803, OS waits 364; RW-excl spins 1300, OS waits 959
------------
TRANSACTIONS
------------
Trx id counter 0 3145870
Purge done for trx's n:o < 0 3141943 undo n:o < 0 0
History list length 22
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0 0, not started, OS thread id 2958192640
MySQL thread id 7942, query id 69073 localhost root
SHOW ENGINE INNODB STATUS
---TRANSACTION 0 3145869, ACTIVE 20 sec, OS thread id 2955325440, thread declared inside InnoDB 343
mysql tables in use 1, locked 1
6 lock struct(s), heap size 1024, 162 row lock(s)
MySQL thread id 7935, query id 69037 localhost root Copying to tmp table
CREATE TABLE 1_temp_foo AS
                       SELECT SQL_NO_CACHE
                           a.*
                       FROM
                           crm_companies AS a
                       LEFT JOIN users b ON a.zipcode = b.uid
                       LEFT JOIN calc_base_materials c ON a.zipcode = c.material_id
                       LEFT JOIN calc_base_material_langtext d ON a.zipcode = d.material_id
                       LEFT JOIN crm_people e ON a.zipcode = e.telephone1_number
                       ORDER BY a.country, a.name1
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (write thread)
Pending normal aio reads: 0, aio writes: 0,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
27579 OS file reads, 613 OS file writes, 392 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 5, seg size 7,
0 inserts, 0 merged recs, 0 merges
Hash table size 34679, node heap has 9 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 1 2030837110
Log flushed up to   1 2030837110
Last checkpoint at  1 2030837110
0 pending log writes, 0 pending chkp writes
231 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 21060366; in additional pool allocated 1048576
Dictionary memory allocated 2897304
Buffer pool size   512
Free buffers       0
Database pages     503
Modified db pages  0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages read 36022, created 166, written 504
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000
--------------
ROW OPERATIONS
--------------
1 queries inside InnoDB, 0 queries in queue
1 read views open inside InnoDB
Main thread id 2957578240, state: waiting for server activity
Number of rows inserted 2022, updated 7, deleted 13, read 528536
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 8.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================

更新2

在查询运行时尝试更新b，c或d时，INNODB STATUS如下：

=====================================
120323 16:12:58 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 27 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 2959, signal count 2957
Mutex spin waits 0, rounds 27587, OS waits 426
RW-shared spins 1321, OS waits 516; RW-excl spins 2578, OS waits 1855
------------
TRANSACTIONS
------------
Trx id counter 0 3145998
Purge done for trx's n:o < 0 3145994 undo n:o < 0 0
History list length 0
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0 0, not started, OS thread id 2958602240
MySQL thread id 7990, query id 69621 localhost root
SHOW INNODB STATUS
---TRANSACTION 0 3145997, ACTIVE 35 sec, OS thread id 2955325440, thread declared inside InnoDB 227
mysql tables in use 1, locked 0
MySQL thread id 7984, query id 69594 localhost root Copying to tmp table
CREATE TABLE 1_temp_foo AS
                       SELECT SQL_NO_CACHE
                           a.*
                       FROM
                           crm_companies AS a
                       LEFT JOIN users b ON a.zipcode = b.uid
                       LEFT JOIN calc_base_materials c ON a.zipcode = c.material_id
                       LEFT JOIN calc_base_material_langtext d ON a.zipcode = d.material_id
                       LEFT JOIN crm_people e ON a.zipcode = e.telephone1_number
                       ORDER BY a.country, a.name1
Trx read view will not see trx with id >= 0 3145998, sees < 0 3145998
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (write thread)
Pending normal aio reads: 0, aio writes: 0,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
54447 OS file reads, 1335 OS file writes, 509 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 5, seg size 7,
584 inserts, 584 merged recs, 4 merges
Hash table size 34679, node heap has 1 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 1 2060137545
Log flushed up to   1 2060137545
Last checkpoint at  1 2060137545
0 pending log writes, 0 pending chkp writes
338 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 20799534; in additional pool allocated 1047808
Dictionary memory allocated 2897304
Buffer pool size   512
Free buffers       0
Database pages     511
Modified db pages  0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages read 70769, created 661, written 3156
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000
--------------
ROW OPERATIONS
--------------
1 queries inside InnoDB, 0 queries in queue
2 read views open inside InnoDB
Main thread id 2957578240, state: waiting for server activity
Number of rows inserted 2022, updated 66643, deleted 13, read 626517
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 7.59 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================

并有实际的公开流程清单

我在您看到这个查询 SHOW INNODB STATUS\G

CREATE TABLE 1_temp_foo AS 
                   SELECT SQL_NO_CACHE 
                       a.* 
                   FROM 
                       crm_companies AS a 
                   LEFT JOIN users b ON a.zipcode = b.uid 
                   LEFT JOIN calc_base_materials c ON a.zipcode = c.material_id 
                   LEFT JOIN calc_base_material_langtext d ON a.zipcode = d.material_id 
                   LEFT JOIN crm_people e ON a.zipcode = e.telephone1_number 
                   ORDER BY a.country, a.name1 

这个查询让我感到毛骨悚然，因为它结合了您可能没有想到的三件事：

• InnoDB的参与基于您的最初前提： Using: MySQL 5.1.41 and InnoDB Tables
• MyISAM也参与其中。为什么要参与MyISAM？所有内部温度表都是MyISAM！生成的联接是一个MyISAM表，在填充临时表后必须将其转换为InnoDB。MyISAM表的默认锁定级别是多少？表级锁定。
• 由于必须创建一个新创建的表，因此需要DDL。直到临时表被填充，转换为InnoDB并最终重命名后，该新表才会出现1_temp_foo。

还有另一个副作用值得注意。当你做

CREATE TABLE tblname AS SELECT ...

结果表没有索引。

我有一些您可能会发现有助于绕过锁定问题的工具。它涉及首先将表制作为一个单独的查询，然后将其填充。制作临时表有两种选择：

选项＃1：尝试创建具有相同布局的表

CREATE TABLE 1_temp_foo LIKE crm_companies;

这将创建表，1_temp_foo使其具有与原始表完全相同的索引和存储引擎crm_companies。

选项2：尝试仅使用相同的存储引擎创建表，但不使用索引。

CREATE TABLE 1_temp_foo SELECT * FROM crm_companies WHERE 1=2;
ALTER TABLE 1_temp_foo ENGINE=InnoDB;

创建表之后（无论选择哪种方式），现在都可以像这样填充表：

INSERT INTO 1_temp_foo
SELECT SQL_NO_CACHE a.*                   
FROM                   
    crm_companies AS a                   
    LEFT JOIN users b ON a.zipcode = b.uid                   
    LEFT JOIN calc_base_materials c ON a.zipcode = c.material_id                   
    LEFT JOIN calc_base_material_langtext d ON a.zipcode = d.material_id                   
    LEFT JOIN crm_people e ON a.zipcode = e.telephone1_number                   
    ORDER BY a.country, a.name
;

现在，此查询应产生行级锁，以使数据可重复读取。换句话说，这是一个事务查询。

警告

选项2优于选项1

• 优势＃1：如果crm_companies具有任何外键约束，则实际上无法实现选项＃1。为了简单起见，您必须选择选项2。
• 优点2：由于选项2创建的表没有用户定义的索引，因此与通过选项1创建表相比，该表的加载速度应更快。

除了将事务隔离级别设置为READ COMMITTED（或READ UNCOMMITTED）之外，还必须将二进制日志格式设置为MIXED或ROW。基于STATEMENT的复制将锁定这种类型的语句，以确保所有内容都是“安全的”。您也可以临时设置innodb_locks_unsafe_for_binlog = 1，但最终可能会导致以这种方式不同步的从属设备。

SET binlog_format = ROW;
CREATE TABLE ... SELECT ...