Just a quick follow-up Jeremy to say your hunch on drop_column :id works
fine. So in the case of my transition from composite pk to a standard id
column, it works like this:
1. In the up
1. drop_constraint :jcus_requirements_orgs_pkey
2. add_primary_key :id
2. In the down
1. drop_column :id (so simple!)
2. add_primary_key [:jcu_id, :requirement_id, :org_id], name:
:jcus_requirements_orgs_pkey
(This with pg and sequel_pg gem)
On Wednesday, September 22, 2021 at 6:48:21 AM UTC-7 John Knapp wrote:
> Thanks for the quick reply Jeremy. It's been my policy for a long while to
> make all migrations reversible. Whether up/down or change, that's the rule
> in our shop. -JK
>
> On Tuesday, September 21, 2021 at 7:14:32 PM UTC-7 Jeremy Evans wrote:
>
>> On Tue, Sep 21, 2021 at 6:31 PM John Knapp <[email protected]> wrote:
>>
>>> Hi,
>>>
>>> I'm transitioning a table from a three way composite PK to a single
>>> integer PK thus:
>>>
>>> 1. In the up:
>>> 1. drop_constraint :jcus_requirements_orgs_pkey
>>> 2. add_primary_key :id
>>> 2. In the down:
>>> 1. drop_constraint :jcus_requirements_pkey, type: :primary_key
>>> 2. add_primary_key [:jcu_id, :requirement_id, :org_id], name:
>>> :jcus_requirements_orgs_pkey
>>>
>>> However, when running the down, the constraint is removed but the column
>>> remains. (Adding a name: :id didn't help but I doubt you're surprised by
>>> that.)
>>>
>>> I wound up adding a drop_column :id in the down block which left me
>>> with a reciprocal up / down migration. (I'm picky that way.)
>>>
>>> But I remain curious if I've missed a more obvious solution (to remove
>>> constraint and the named column in a single step) or if this is a bug. So .
>>> . . I thought I'd ask. :-)
>>>
>>
>> Depending on the database, you could try just the drop_column and see if
>> it also removes the constraint. However, I think the most portable
>> approach is the one you already have with both the drop_constraint and the
>> drop_column.
>>
>> Don't fear separate up/down migrations. Over 90% of the migrations in my
>> production applications use up/down and not change.
>>
>> Thanks,
>> Jeremy
>>
>
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