maz

maz

I have a query containing a relatively complicated join and there are 85 items total.

Strangely, after sending the second after cursor no more items return(Paginator never returns more than 60 items).

This is the query:

  defp list_media_items_by_channel_slug_query(channel_slug, :feed) do
    from(m in MediaItem,
      join: con in ContentMediaItems,
      on: m.id == con.media_item_id,
      join: chan in assoc(con, :channel),
      where: chan.slug == ^channel_slug,
      preload: [:mediaitemartifacts],
      order_by: [{:desc, :inserted_at}]
    )
  end

Called like:

        %{entries: entries, metadata: metadata} =
          Repo.paginate(
            query,
            include_total_count: true,
            after: after_cursor,
            sort_direction: sort_direction,
            cursor_fields: cursor_fields,
            limit: 30
          )

The first cursor returns another 30, but the second cursor returns nothing, but when I get the full list there are 85 items(so the cursor should return 25, but actually returns 0).

Repo.all(query) # returns 85

I’m baffled. The 25 items are there but I don’t get them returned?

Elixir 1.16.1 (compiled with Erlang/OTP 26)
ecto 3.11.2
paginator, 1.1.0

Showing Posts 1 to 4

al2o3cr

al2o3cr

What values are being passed here? What SQL gets executed?

The described symptom makes me suspect that something is misaligned, so that the “next” page isn’t using the right query.

maz

maz OP

It looks like this:

        %{entries: entries, metadata: metadata} =
          Repo.paginate(
            query,
            include_total_count: true,
            after: after_cursor,
            sort_direction: :desc,
            cursor_fields: [:inserted_at],
            limit: 30
          )
maz

maz OP

So if I sort by title I don’t see the same problem. Is it possible that if there are inserted_at dates that are identical/very similar the cursor can start to fail?

maz

maz OP

I found a fix, and you led me down the trail, thanks.

cursor_fields: [:inserted_at, :title],

If I use these two columns, it gives the paginator enough to work with and I receive the correct result sets. I think a lot of the inserted_at dates are too similar.

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