Array support

[thure]

I've appreciated this library a ton.

Seems however that it's missing or now needs to implement array support for lquery and possibly ltree in order to support operations that take arrays as arguments: elixir-ecto/postgrex#528.

I'd be willlilng to help, but I'm totally unfamiliar with how Postgres communicates with Ecto. Is there a model for encoding/decoding arrays of this type I could use to create a PR, if one would be welcome?

[josemrb]

Hi @thure

Thanks for the report, I didn't know about this problem.

Seems however that it's missing or now needs to implement array support for lquery and possibly ltree in order to support operations that take arrays as arguments: elixir-ecto/postgrex#528.

Can you show me an example query with this issue?

I'd be willlilng to help, but I'm totally unfamiliar with how Postgres communicates with Ecto. Is there a model for encoding/decoding arrays of this type I could use to create a PR, if one would be welcome?

I'm still not sure what needs to be done but PRs are welcome :)

[thure]

Can you show me an example query with this issue?

If I use code like this:

lqueries = ["some.path", "other.path"]
from(
   bt in BallotTree,
   where: fragment("? \\? ?", bt.path, ^lqueries),
   select: sum(bt.vote_power)
 )
 |> Repo.all()

It gets translated to this SQL:

SELECT sum(c0."vote_power") FROM "cached_stv_scott_ballot_trees" AS c0 WHERE (c0."path" ? $2) [["some.path", "other.path"]]

But it errors with:

[error] Postgrex.Protocol (#PID<0.1320.0>) disconnected: ** (Postgrex.QueryError) type `_lquery` can not be handled by the types module Accord.PostgresTypes

…which seems like it knows that this is an array of the correct type, given Postgres prepends a type with an underscore in those cases, it just doesn't handle encoding/decoding arrays of these types.

Has EctoLtree been tested with ltree array opererators like ?, <@, etc?

[warmwaffles]

I've been digging into this issue and I think it's not going to be possible.

I'm fairly certain, it will need an upstream addition to postgrex to fix the _ prefixing issue.

[gaslit]

Hello, may i know if this issue is fixable w a PR as above? Many thanks