Paginator ignores sort direction

Questions / Help
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1

I’m using the Paginator library and right before calling Repo.paginate(), I print the query which is:

Query: #Ecto.Query<from c0 in Amplify.Models.ContestEntry,
 where: c0.contest_id == ^"2", where: not is_nil(c0.prize_id),
 order_by: [desc: c0.inserted_at]>

This makes sense to me, but when I call paginate, it executes:

SELECT ... 
FROM "contest_entries" AS c0 
WHERE (c0."contest_id" = $1) AND (NOT (c0."prize_id" IS NULL)) AND (c0."inserted_at" < $2) 
ORDER BY c0."inserted_at" LIMIT $3 [2, ~U[2024-09-26 19:10:25Z], 4]

Notice that the executed ORDER BY does not have the DESC associated with it.

Could this be because I am passing before to paginator and it defaults to an ASC sort in that case when I really want a DESC sort? If so, how does Paginator handle traversing through a list sorted in reverse?

2

I believe Paginator has been abandoned, and it is generally recommended that you migrate your code to Flop.

3

Thank you. I switched to Flop and am getting similar behaviour:

Query before being executed:

#Ecto.Query<from c0 in Amplify.Models.ContestEntry,
 where: c0.contest_id == ^"2", where: not is_nil(c0.prize_id)>

Flop parameters:

%{
  "after" => nil,
  "before" => nil,
  "first" => 3,
  "order_by" => ["inserted_at"],
  "order_direction" => ["desc"]
}

How I’m calling it:

Flop.validate_and_run(query, params)

Actual query that’s run:

SELECT ... 
FROM "contest_entries" AS c0 WHERE (c0."contest_id" = $1) AND (NOT (c0."prize_id" IS NULL)) 
ORDER BY c0."inserted_at" LIMIT $2 [2, 4]

I expect it to execute ORDER BY c0."inserted_at" DESC but it’s not adding the DESC part.

4

If you’re just doing offset/limit or keyset why not just write it yourself?

5

I’m not using limit/offset. I want to use cursor based paging.