#2872 sqlite3 adapter drops :decimal columns precision & scale when migration tries to alter them - Ruby on Rails

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#2872 incomplete

sqlite3 adapter drops :decimal columns precision & scale when migration tries to alter them

Reported by Andrey "Zed" Zaikin | July 6th, 2009 @ 10:42 AM | in 3.0.6

example migrations:

class M1 < ActiveRecord::Migration
  def self.up

create_table 'users' do |t|
  t.string 'name'
  t.decimal 'v1', :precision =&gt; 10, :scale =&gt; 3
end




  end



  def self.down

drop_table 'users'




  end
end



class M2 < ActiveRecord::Migration
  def self.up

change_column :users, :v1, :decimal, :precision =&gt; 12, :scale =&gt; 5




  end



  def self.down
  end
end

expected resulting schema:

ActiveRecord::Schema.define(:version => 20090706090649) do
  create_table "users", :force => true do |t|

t.string  &quot;name&quot;
t.decimal &quot;v1&quot;,   :precision =&gt; 12, :scale =&gt; 5




  end
end

actual resulting schema:

ActiveRecord::Schema.define(:version => 20090706090649) do
  create_table "users", :force => true do |t|

t.string  &quot;name&quot;
t.decimal &quot;v1&quot;




  end
end

Comments and changes to this ticket

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Andrey "Zed" Zaikin July 6th, 2009 @ 10:46 AM
- Tag changed from “migrations, patch, schema, sqlite3” to “activerecord, active_record, migrations, patch, schema, sqlite3”
- rails_sqlite3_decimal_precision.diff 819 Bytes
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Taryn July 6th, 2009 @ 10:49 AM
I've hit this problem too.
Looking into the sqlite adaptor code, you can see that it's simply dropping any+all options.
Yehuda Katz (wycats) July 8th, 2009 @ 12:12 AM
- Milestone cleared.
- State changed from “new” to “incomplete”
- Assigned user set to “Yehuda Katz (wycats)”
Any chance I could get you to include a new test case for this?
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Paul Hinze July 20th, 2009 @ 07:43 PM
Here's a test case that fails without the above patch and passes when it is applied. It tests that you can use change_column to alter a column's scale and precision. The attributes are dropped in the code without this patch, and they are properly changed when it is applied.
- test_change_column_does_not_lose_decimal_precision_and_scale.patch 1.1 KB
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Taryn East July 22nd, 2009 @ 12:19 PM
Ok, when I click on Paul's patch I get some sort of key error, so here's my own patch that includes a test that fails with the current Rails code, as well as Adnrey's code - which makes it pass.

Note - I've made the test-case specific to sqlite3 as that's where the issue is located.
- sqlite_adapter_precision_scale_patch.diff 3 KB
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Taryn East July 22nd, 2009 @ 12:27 PM
I meant to add... but technically the test should pass on all adapters. Only I can't test Postgres - because I don't have that installed.
it runs fine for all the other standard adapters ie it doesn't fail when I remove the adapter-check line except for the postgres section which doesn't run at all.
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Taryn East July 22nd, 2009 @ 01:27 PM
Ok - that's weird. Looks like running a migration with this sets the local values for precision/scale... but doesn't actually change the real db properly.
You can test that with a migration that changes two columns' precisions:

class M£ < ActiveRecord::Migration
def self.up
```
change_column :users, :v1, :decimal, :precision => 12, :scale => 5
change_column :users, :v2, :decimal, :precision => 12, :scale => 5
```
end

def self.down end end

expected resulting schema:

ActiveRecord::Schema.define(:version => 20090706090649) do
create_table "users", :force => true do |t|
```
t.string  "name"
t.decimal "v1",   :precision => 12, :scale => 5
t.decimal "v2",   :precision => 12, :scale => 5
```
end end

actual resulting schema:

ActiveRecord::Schema.define(:version => 20090706090649) do
create_table "users", :force => true do |t|
```
t.string  "name"
t.decimal "v1"
t.decimal "v2",   :precision => 12, :scale => 5
```
end end

If you reverse the order of two change_column names in the migration... you get:

ActiveRecord::Schema.define(:version => 20090706090649) do
create_table "users", :force => true do |t|
```
t.string  "name"
t.decimal "v1",   :precision => 12, :scale => 5
t.decimal "v2"
```
end end

ie - only the last migration seems to actually change the schema...
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Taryn East July 22nd, 2009 @ 01:28 PM
hmmm... and "edit last comment" feature would be appreciated.. ;)
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Taryn East July 22nd, 2009 @ 05:04 PM
Hokay... so after much digging there is one important fact we need to remember.
SQLite doesn't actually (natively) support :precision/scale.

The troubles that my company ran into were more based on the fact that in doing the migration... the schema lost the precision/scale - which means that when we uploaded into a NON-sqlite instance of the db... we then ran into issues.

I'm not sure how to test for this as we don't have Rails tests (that I see) where we dump the schema from one adaptor, then try to schema:load into another.

In any case, I ran across one other place where the precision/scale are "lost" in the sqlite adaptor... adding the following patch seemed to solve that... but I can't officially test it.

Any comments/suggestions welcome.
- precision_scale_patch_two.diff 724 Bytes
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Matt Kern August 7th, 2009 @ 12:54 AM
So if I understand this correctly, the schema should retain the precision and scale, but the sqlite3 adapter should ignore it when creating the columns, correct?
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Bryce Thornton August 9th, 2009 @ 08:38 PM
I've ran into this as well. Yes, it would be nice for the schema to retain the precision and scale for when we actually load it on a production database.
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Matt Kern August 9th, 2009 @ 08:51 PM
I think it's more than nice, it's required. The recommendation to load from schema rather than running thru the migrations on a production deploy or any new instance deploy makes this pretty high priority.
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Taryn East August 10th, 2009 @ 10:47 AM
Matt - yep - that's the ticket.
The patches I've submitted do this now.

We ran into the issue because during testing we used Sqlite - but production (of course) is on a real db... and loading the schema started causing all sorts of truncation errors in our money columns :P
Dan Pickett May 9th, 2010 @ 06:23 PM
- Tag changed from “activerecord, active_record, migrations, patch, schema, sqlite3” to “activerecord, active_record, bugmash, migrations, patch, schema, sqlite3”
Jeremy Kemper August 30th, 2010 @ 04:10 AM
- Milestone cleared.
- Importance changed from “” to “”
[bulk edit]
Ryan Bigg October 9th, 2010 @ 10:02 PM
- Tag cleared.
Automatic cleanup of spam.
Jeff Kreeftmeijer October 10th, 2010 @ 01:04 PM
- Title changed from “[PATCH] sqlite3 adapter drops :decimal columns precision & scale when migration tries to alter them” to “sqlite3 adapter drops :decimal columns precision & scale when migration tries to alter them”
- Tag set to “activerecord, patch, sqlite3”
Using the "patch" tag instead of prefixing the ticket title with "[PATCH]" to make sure patched tickets end up in the open patches bin. :)
Jeremy Kemper October 15th, 2010 @ 11:01 PM
- Milestone set to “3.0.2”
[bulk edit]
Jeff Kreeftmeijer November 7th, 2010 @ 04:53 PM
- Tag cleared.
Automatic cleanup of spam.
Santiago Pastorino November 15th, 2010 @ 09:04 PM
- Milestone cleared.
[bulk edit]
Santiago Pastorino February 12th, 2011 @ 09:58 PM
- Milestone set to “3.0.5”
[bulk edit]
Santiago Pastorino February 27th, 2011 @ 03:15 AM
- Milestone changed from “3.0.5” to “3.0.6”
[bulk edit]