For a primary key of an integral type, why is it important to avoid gaps ?

Posted by Jacques René Mesrine on Stack Overflow See other posts from Stack Overflow or by Jacques René Mesrine
Published on 2010-03-29T02:27:46Z Indexed on 2010/03/29 2:33 UTC
Read the original article Hit count: 582

Filed under:

mysql

|

indexing

I am generating a surrogate key for a table & due to my hi/lo algorithm, everytime you reboot/restart the machine, gaps may appear.

T1: current hi = 10000000 
    (sequence being dished out .. 1 to 100)
       Assume that current sequence is 10000050

T2: restart system.

T3: System gives out the next_hi as 10000100 
    (sequence being dished out now ranges from 101 to 200)

T4: Next request for a key returns 100001001

From a primary key or indexing internals perspective, why is it important that there be no gaps in the sequences ? I'm asking this for a deeper understanding of mysql specifically.

Thanks

© Stack Overflow or respective owner

Related posts about mysql

How to remove MySQL completely with config and library files on ubuntu 12.04 gnome 3.0

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I tried everything till now: sudo apt-get remove mysql-server mysql-client mysql-common sudo apt-get purge mysql-server mysql-client mysql-common sudo apt-get autoremove and even more commands... But whenever I am trying to locate mysql. I get a no. of files related to mysql command: shell>>… >>> More
mysql: Cannot load from mysql.proc. The table is probably corrupted

as seen on Server Fault - Search for 'Server Fault'
Mysql was started: /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 but when I'm trying to do something: ERROR 1548 (HY000) at line 1: Cannot… >>> More
Why is there a /etc/init.d/mysql file on this Slackware machine? How could it have gotten there?

as seen on Server Fault - Search for 'Server Fault'
A client of my IT-consulting service owns a web-development shop. He's been having problems with a Slackware 12.0 server running MySQL 5.0.67. The machine was set up by the client's sysadmin, who left on bad terms. My client no longer employs a sysadmin. As far as I can tell, the only copy of MySQL… >>> More
mysql: Bind on unix socket: Permission denied

as seen on Server Fault - Search for 'Server Fault'
Can't start mysql with: sudo /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 120222 13:40:48 mysqld_safe Starting mysqld daemon with databases… >>> More
MySQL – Learning MySQL Online in 6 Hours – MySQL Fundamentals in 320 Minutes

as seen on SQL Authority - Search for 'SQL Authority'
MySQL is one of the most popular database language and I have been recently working with it a lot. Data have no barrier and every database have their own place. I have been working with MySQL for quite a while and just like SQL Server, I often find lots of people asking me if I have a tutorial which… >>> More

Related posts about indexing

Outlook 2007 OST File Indexing and OneNote 2007 Indexing are Broken

as seen on Super User - Search for 'Super User'
I'm running Outlook 2007 under Windows 7 Home Premium RTM. My OST file was previously being properly indexed but eventually searches significantly slowed down so I suspected a problem. Searching and indexing appears broken in OneNote 2007 as well as search time is now significantly longer. I brought… >>> More
IIS6 Indexing Service indexing asp.net codebehind (.aspx.cs) files

as seen on Server Fault - Search for 'Server Fault'
I've setup a few catalogs on an Windows Server 2003 IIS6 install, each tracking files within a website. In the Properties - Generation Dialog for each catalog, 'Index files with unknown extensions' is turned OFF. 'Inherit above settings from Service' in that dialog is also turned off. However, the… >>> More
Indexing vs. no indexing when inserting records

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a few questions about whether or not it would be best to not use indexing. BACKGROUND: My records have a timestamp attribute, and the records will be inserted in order of their timestamps (i.e., inserted chronologically). QUESTIONS: If I DON'T use indexing is it typical for the database… >>> More
SQL SERVER – Transcript of Learning SQL Server Performance: Indexing Basics – Interview of Vinod Kumar by Pinal Dave

as seen on SQL Authority - Search for 'SQL Authority'
Recently I just wrote a blog post on about Learning SQL Server Performance: Indexing Basics and I received lots of request that if we can share some insight into the course. Here is 200 seconds interview of Vinod Kumar I took right after completing the course. We have few free codes to watch the course… >>> More
Can the Windows Indexing Service restart an app pool if it doesn't index the Web.Config?

as seen on Stack Overflow - Search for 'Stack Overflow'
I am having a slight debate with a colleague of mine on this subject. Scenario: A web site has a sub directory that is indexed using the Windows Indexing Service. There is not a web.config in this directory and the indexing service is not indexing the parent directory which is the site root. Something… >>> More