Once and for all: Rails migrations integer :limit option | Ariejan.net

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Once and for all: Rails migrations integer :limit option

I literally always have to look up the meaning of :limit in migrations when it comes to integer values. Here’s an overview. Now let’s memorise it (oh, this works for MySQL, other databases may work differently):

:limit	Numeric Type	Column Size	Max value
1	tinyint	1 byte	127
2	smallint	2 bytes	32767
3	mediumint	3 byte	8388607
nil, 4, 11	int(11)	4 byte	2147483647
5..8	bitint	8 byte	9223372036854775807

Note: by default MySQL uses signed integers and Rails has no way (that I know of) to change this behaviour. Subsequently, the max. values noted are for signed integers.

Tags: integer, limit, migrations, MySQL, Rails, sql

This entry was posted on Thursday, August 20th, 2009 at 16:25 and is filed under Ruby on Rails. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “Once and for all: Rails migrations integer :limit option”

Ariejan de Vroom says:
21 August, 2009 at 14:49
FYI: Choosing your column sizes correctly can improve MySQL performance dramatically.
Ciaran Lee says:
3 October, 2009 at 18:33
Oh cool, this really helped me – thanks!
Mark Richman says:
1 January, 2010 at 23:42
THANKS! This is really useful – where can I find this in the Rails API docs?

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