Ecto get_by returns nil?

Questions / Help
1

Why does Ecto’s Repo.get_by returns nil. Example

dizzy = Repo.get_by(Artist, name: "Dizzy Gillespie")

iex(1) dizzy
nil
2

So if you’re on Ecto 3.x (I’m looking at Ecto 3.2.5 documentation now), Repo.get_by returns nil under the following condition:

Returns nil if no result was found. Raises if more than one entry.

This means that your database doesn’t contain an “Artist” with an entry whose name is Dizzy Gillespie.

3

Can you do a Repo.all to see what data you have in the Artists table?

4

I just added an Artist with,

Repo.insert(%Artist{name: "Dizzy Gillespie"})

Then checked by
Repo.aggregate(Artist, ;count, :id)

and indeed it was added. So it contains the artist. Still the get_by result is nil.

5

Yes it’s all there, but why the variable containing the result of Repo.get_by returns nil?

6

Are you sure that there was no other entry in the DB? What is the return value od Repo.all(Artist)?

7

Isn’t there some tricky utf8 character somewhere?

8

Like I said the expected values are there, just wondering the meaning of get_by 's return value of nil?

9

@treble37 pointed you to the documentation fragment:

Returns nil if no result was found. Raises if more than one entry.

What do you want to know more?

1 Like
10

There is exactly 1 matching entry, so why nil?

11

If it’s nil then there is not one matching entry, something about the lookup is incorrect.