fireproofsocks

fireproofsocks

Forgive me if this is obvious, but how does one delete a database record WITHOUT selecting it first? Ecto.Repo — Ecto v3.14.0 has examples, but they are all doing 2 operations: a select, then a delete.

In the interest of optimization, is it possible with Ecto to delete a record with a single operation? Something like the SQL query DELETE FROM my_table WHERE id=123 ?

Is it considered bad form to delete without selecting first?

Thanks for pointers, as always.

Showing Posts 1 to 8

Adzz

Adzz

Ypu can do something like this:

%MyStruct{id: 10} |> MyApp.Repo.delete

That is just build a struct with the id in it then delete

OvermindDL1

OvermindDL1

Can also look at repo.delete_all/2, it accepts a query for doing just that. :slight_smile:

xlphs

xlphs

from(x in DataModel, where: x.id == ^id) |> Repo.delete_all

fireproofsocks

fireproofsocks OP

I tried that, but that generates an error:
** (Ecto.StaleEntryError) attempted to delete a stale struct

Adzz

Adzz

I think that will only do that if the id you gave it doesn’t exist in the db… maybe it was already deleted?

OvermindDL1

OvermindDL1

From the docs:

If the struct has been removed from db prior to call, Ecto.StaleEntryError will be raised.

So yep, looks like you are right. :slight_smile:

fireproofsocks

fireproofsocks OP

Thank you! Just to show a more thorough example:

{rows_deleted, _} = from(x in DataModel, where: x.id == ^id) |>; Repo.delete_all

You might get zero as the number of rows deleted.

Huolong

Huolong

I think you have to do a query to pass existing rows to delete or delete_all,
because they require the Ecto metadata element of the struct to contain the ‘loaded’ flag.
The only alternative would be to completely fake the whole struct,
including all the internal fields and flags.

But I agree with you that there should be a version of delete,
which just takes a primary key value, by analogy with the ‘get’ function.

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