Instagram的Postgres为Sharding实现自定义ID的方法很棒，但我需要在MySQL中实现。
所以，我转换了这个博客底部的方法，在这里：http://instagram-engineering.tumblr.com/post/10853187575/sharding-ids-at-instagram
MySQL版本：
CREATE TRIGGER shard_insert BEFORE INSERT ON tablename
FOR EACH ROW BEGIN
DECLARE seq_id BIGINT;
DECLARE now_millis BIGINT;
DECLARE our_epoch BIGINT DEFAULT 1314220021721;
DECLARE shard_id INT DEFAULT 1;
SET now_millis = (SELECT UNIX_TIMESTAMP(NOW(3)) * 1000);
SET seq_id = (SELECT AUTO_INCREMENT FROM information_schema.TABLES WHERE TABLE_SCHEMA = "dbname" AND TABLE_NAME = "tablename");
SET NEW.id = (SELECT ((now_millis - our_epoch) << 23) | (shard_id << 10) | (SELECT MOD(seq_id, 1024)));
END
该表大致如下：
CREATE TABLE tablename (
id BIGINT AUTO_INCREMENT,
...
)
问题：
我尝试创建一个新表格，例如＆＃34; tablename_seq＆＃34;，有一行，一个用于存储我自己的auto_increment值的计数器，然后在TRIGGER中对该表进行更新，但问题是我无法在存储过程中锁定表（触发器），所以我有完全相同的问题，我不能保证计数器在触发器之间是唯一的：（。
我很难过，真的很感激任何提示！
可能的解决方案：
答案 0 :(得分：2)
以下SQL Fiddle生成如下所示的输出：
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 45
Server version: 5.5.35-1
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select `id` from `tablename`;
+-------------------+
| id |
+-------------------+
| 11829806563853313 |
| 11829806563853314 |
| 11829806563853315 |
| 11829806563853316 |
| 11829806563853317 |
| 11829806563853318 |
| 11829806563853319 |
| 11829806563853320 |
| 11829806563853321 |
| 11829806563853322 |
| 11829806563853323 |
| 11829806563853324 |
| 11829806563853325 |
| 11829806563853326 |
| 11829806563853327 |
| 11829806563853328 |
| 11829806563853329 |
| 11829806563853330 |
| 11829806563853331 |
| 11829806563853332 |
| 11829806563853333 |
| 11829806563853334 |
| 11829806563853335 |
| 11829806563853336 |
| 11829806563853337 |
| 11829806563853338 |
| 11829806563853339 |
| 11829806563853340 |
| 11829806563853341 |
| 11829806563853342 |
| 11829806563853343 |
| 11829806563853344 |
| 11829806563853345 |
| 11829806563853346 |
| 11829806563853347 |
| 11829806563853348 |
| 11829806563853349 |
| 11829806563853350 |
| 11829806563853351 |
| 11829806563853352 |
+-------------------+
40 rows in set (0.01 sec)
如果能真正解决您的需求，请接受答案。
<强>更新
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 46
Server version: 5.5.35-1
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> DELIMITER //
mysql> DROP FUNCTION IF EXISTS `nextval`//
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> DROP TRIGGER IF EXISTS `shard_insert`//
Query OK, 0 rows affected (0.00 sec)
mysql> DROP TABLE IF EXISTS `tablename_seq`, `tablename`;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE `tablename_seq` (
-> `seq` BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY
-> )//
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE `tablename` (
-> `id` BIGINT UNSIGNED PRIMARY KEY
-> )//
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE FUNCTION `nextval`()
-> RETURNS BIGINT UNSIGNED
-> DETERMINISTIC
-> BEGIN
-> DECLARE `_last_insert_id` BIGINT UNSIGNED;
-> INSERT INTO `tablename_seq` VALUES (NULL);
-> SET `_last_insert_id` := LAST_INSERT_ID();
-> DELETE FROM `tablename_seq`
-> WHERE `seq` = `_last_insert_id`;
-> RETURN `_last_insert_id`;
-> END//
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TRIGGER `shard_insert` BEFORE INSERT ON `tablename`
-> FOR EACH ROW
-> BEGIN
-> DECLARE `seq_id`, `now_millis` BIGINT UNSIGNED;
-> DECLARE `our_epoch` BIGINT UNSIGNED DEFAULT 1314220021721;
-> DECLARE `shard_id` INT UNSIGNED DEFAULT 1;
-> SET `now_millis` := `our_epoch` + UNIX_TIMESTAMP();
-> SET `seq_id` := `nextval`();
-> SET NEW.`id` := (SELECT (`now_millis` - `our_epoch`) << 23 |
-> `shard_id` << 10 |
-> MOD(`seq_id`, 1024)
-> );
-> END//
Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO `tablename`
-> VALUES
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0),
-> (0), (0), (0), (0), (0)//
Query OK, 40 rows affected (0.00 sec)
Records: 40 Duplicates: 0 Warnings: 0
mysql> DELIMITER ;
mysql> SELECT `id` FROM `tablename`;
+-------------------+
| id |
+-------------------+
| 12581084357198849 |
| 12581084357198850 |
| 12581084357198851 |
| 12581084357198852 |
| 12581084357198853 |
| 12581084357198854 |
| 12581084357198855 |
| 12581084357198856 |
| 12581084357198857 |
| 12581084357198858 |
| 12581084357198859 |
| 12581084357198860 |
| 12581084357198861 |
| 12581084357198862 |
| 12581084357198863 |
| 12581084357198864 |
| 12581084357198865 |
| 12581084357198866 |
| 12581084357198867 |
| 12581084357198868 |
| 12581084357198869 |
| 12581084357198870 |
| 12581084357198871 |
| 12581084357198872 |
| 12581084357198873 |
| 12581084357198874 |
| 12581084357198875 |
| 12581084357198876 |
| 12581084357198877 |
| 12581084357198878 |
| 12581084357198879 |
| 12581084357198880 |
| 12581084357198881 |
| 12581084357198882 |
| 12581084357198883 |
| 12581084357198884 |
| 12581084357198885 |
| 12581084357198886 |
| 12581084357198887 |
| 12581084357198888 |
+-------------------+
40 rows in set (0.00 sec)
请参阅db-fiddle。
答案 1 :(得分：2)
另一种方法是获取自动增量数字块。如果将MySQL auto increment increment设置为1000，则进程可以在“序列”表中执行插入并获取自动增量值。然后，该进程知道它可以使用1000个连续数字，从该数字开始，将没有冲突。如果你要录制的只是一个数字，则无需在中央表中记录每个增量。
除了自动增量偏移之外，这在多个主设置中最常用。你也可以去多个主路线，并插入不同的主人。自动增量增量和偏移量将确保没有冲突。这需要扎实的MySQL复制知识。