How Flickr generates a unique ID (translated)

Source: Internet
Author: User
Tags stub unique id

How Flickr generates a unique ID, a GUID. Consistency Hash. are not, use the MySQL key automatically increment can.

There is a nonstandard extension in MySQL, the syntax is replace into, although inert on DUPLICATE KEY update also has the same functionality, but replace into is still supported.

Flickr uses the replace into to generate a globally unique ID.

REPLACE works exactly like inserts, except that if the "if" in the "table has" same value as a new row for a PRIMARY KE Y or a UNIQUE index, the old row was deleted before the new row is inserted.

The TICKETS64 schema looks like:

CREATE TABLE ' Tickets64 ' (
  ' id ' bigint () unsigned not null auto_increment,
  ' stub ' char (1) NOT null default ', 
  primary key  (' ID '), the
  UNIQUE key ' stub ' (' Stub ')
Engine=myisam              #这里创建了一个表, specifically used to generate key

SELECT * FROM Tickets64 returns a single row that looks something like:

| id |                stub |
| 72157623227190423 |    A |

When I need a new globally unique 64-bit ID I issue the following SQL:

REPLACE into Tickets64 (stub) VALUES (' a ');
SELECT last_insert_id ();     #每次需要获取key的时候, executing this query, you can get a different key, which is the return value of last_insert_id ()
  They then used 2 of these servers to rotate the key, and each server's auto-increment-increment and Auto-increment-offset were different. The global unique key was born like this, but I'm still a little skeptical of the force as the author says. The author finally said that this thing from 2006 to now work shcokingly ... Try it this way when you need it. Original link:

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.