Rails 3 Migration with longtext

Question

I am needing to change a column type from text to longtext in my Rails script, but can't find anything on how to do this.

Has anyone ran across this?

Thanks! Dennis

(for rails 2 at least, you can just specify type :longtext FWIW) — rogerdpack, May 21 '14 at 18:13

Chuck Callebs · Accepted Answer · 2013-10-14T15:25:00.477

193

The text type handles tinytext, text, mediumtext, and longtext for MySQL, if that's what you're using. Just specify the upper bound using :limit => ...

Example:

change_column :articles, :body, :text, :limit => 4294967295

The default value of limit is 65535, as expected.

1 to 255 bytes: TINYTEXT
256 to 65535 bytes: TEXT
65536 to 16777215 bytes: MEDIUMTEXT
16777216 to 4294967295 bytes: LONGTEXT

The MySQL documentation can be found here.

edited Oct 14 '13 at 15:25

answered Dec 14 '10 at 19:50

Chuck Callebs

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What happens if you don't know the limit? – dennismonsewicz Dec 14 '10 at 19:51
Updated with a comprehensive list. – Chuck Callebs Dec 14 '10 at 20:40
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It should be "4294967295" and not "4294967296" (i.e., `4.gigabytes - 1`) or else `Mysql2::Error: Display width out of range for column ....` is raised. – Vikrant Chaudhary Apr 19 '11 at 10:49
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I've modified my answer to reflect that. Thanks a bunch Vikrant. – Chuck Callebs Apr 19 '11 at 13:09
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On mysql 5.1.52 I used a limit of `16.megabytes - 1`, but I still got a longtext, not a mediumtext. Any idea why? Thanks. – David M. Nov 10 '11 at 01:03
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Same for me, even though specifying t.text "bla", :limit => 16777215 , the resulting column type is "longtext". – Martin T. Jan 17 '12 at 16:50
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All: This was a bug in Rails. It has been patched as of a few weeks ago in the 4.0 branch. – Chuck Callebs May 09 '12 at 18:23
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@ChuckCallebs: Could we get a link to the PR that fixed this issue and what version of Rails it's supposed to be shipped in? – Damien Wilson Jan 27 '15 at 00:55
How do I get the max limit? can I do `:limit => :max`? I'm trying to get an equivalent of SQL server's `NVARCHAR(MAX)` but I am migrating to postgres – David West Mar 29 '17 at 20:10
As noted by @DavidM. above, the different MySQL TEXT data types have different sized overheads. http://rricketts.com/mysql-difference-tinytext-text-mediumtext-longtext/ has a handy table for reference. – maurice Jan 24 '18 at 00:40

Rails 3 Migration with longtext

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