prkhrkat
I have a table in which I have put unique constraints on the combination of two fields. I had also defined this in changeset.
def changeset(asset, attrs) do
asset
|> cast(attrs, @create_attrs)
|> validate_required(@required_attrs)
|> unique_constraint([:serial_number, :organization_id])
end
But I keep getting this error instead of the object {:error, #Ecto.Changeset…} -
Server: localhost:4000 (http)
Request: POST /api/create_asset
** (exit) an exception was raised:
** (Ecto.ConstraintError) constraint error when attempting to insert struct:
* "assets_organization_id_serial_number_index" (unique_constraint)
If you would like to stop this constraint violation from raising an
exception and instead add it as an error to your changeset, please
call `unique_constraint/3` on your changeset with the constraint
`:name` as an option.
Until I found out that order also matters when writing the unique_constraint. It worked when i changed it to -
unique_constraint([:organization_id, :serial_number])
So I just wanted to put it here, so that we can fix this bug in the new release. Would also love to contribute if I’m able to fix it by myself.
Thanks
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sodapopcan
This isn’t a bug, the “order” matters at the database level too. Ecto is using
:org_idand:serial_numberto create the name of the index. Otherwise, the order of compound indexes, at least in postgres, does matter.al2o3cr
The default behavior of
unique_constraintis tripping you up here:organization_idfirst in the index makes sense since Postgres can use partial indexes from the left-hand side.serial_numberfirst in theunique_constraintcall makes sense too, since you likely want the “is already taken” message on the serial number rather than the organization ID.One or the other of these has to change. Either:
unique_constraintthe correct name of the index to use with thename: "assets_organization_id_serial_number_index"optionunique_constraintin the same order as the index (so the name can be automatically generated), then tell it to put the error onserial_numberinstead witherror_keyprkhrkat
Thanks @sodapopcan and @al2o3cr It makes sense.