Martijn Tonies wrote:
Connie,
I have a database for ASN information in which I save asn information for
reference by other scripts (asn lookup can be expensive).
CREATE TABLE `ASNINFO` (
`asnInfoID` int(11) NOT NULL auto_increment,
`asNumber` int(11) NOT NULL default '0',
`description` varchar(255) default NULL,
`comment` varchar(255) default NULL,
`f_time_stamp` timestamp NOT NULL default CURRENT_TIMESTAMP on update
CURRENT_TIMESTAMP,
PRIMARY KEY (`asnInfoID`),
UNIQUE KEY `asNumber` (`asNumber`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
Multiple Ips can share the same ASN value.
Is it better to do an 'insert ignore' into ASNINFO when I have to look one
up, or is it better to try to fetch the ASN information to see if it exists,
and then if it does not exist, do the insert. I figure the fetch is one sql
command, and the insert is one sql command, so if an asn does not exist, it
is two data base accesses, where if I do an 'insert ignore' it is only one
command and if the value is in the table, the insert is ignored.
The "insert ignore" sounds a bit hackish to me.
Given that "asNumber" is indexed via the unique key, it will be fast anyway.
That being said, it is entirely possible that someone will insert the
row you are looking for between your first select and the insert
in case you didn't find it. So you would have to handle that case
anyway.
Martijn Tonies
Database Workbench - development tool for MySQL, and more!
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
Database development questions? Check the forum!
http://www.databasedevelopmentforum.com
So, for my peace of mind, I would need to follow these procedures to
ensure Martijn's issue doesn't happen:
1. lock the table
2. execute my select
3. insert if it does not already exist
4. unlock the table
On a high level, is this a correct list of procedures?
Sean
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