Update query transformation issue

[LostKobrakai]

Elixir version

1.17.2

Database and Version

sqlite 3 (as brought by adapter)

Ecto Versions

3.12.1

Database Adapter and Versions (postgrex, myxql, etc)

exqlite 0.23, ecto_sqlite3 0.17.0

Current behavior

The below query doing left joins is turned into multiple FROM clauses, which according to the sqlite docs stating they modeled it after postgres and postgres documenting it to be a cross join, would be a different kind of join.

#Ecto.Query<from p0 in Planner.ProjectsQwer.Project,
 left_join: q1 in subquery(from q0 in "qwer_placeables",
  where: q0.project_id == ^1,
  group_by: [fragment("TRUE")],
  select: %{
  json:
    fragment(
      "json_group_array(?)",
      fragment(
        "json_object(?,?,?,?,?,?,?,?,?,?,?,?,?,?)", […fields]
      )
    )
}),
 as: :placeables, on: true,
 left_join: q2 in subquery(from q0 in "qwer_links",
  where: q0.project_id == ^1,
  group_by: [fragment("TRUE")],
  select: %{
  json:
    fragment(
      "json_group_array(?)",
      fragment(
        "json_object(?,?,?,?,?,?,?,?,?,?,?,?)", […fields]
      )
    )
}),
 as: :links, on: true, where: p0.id == ^1,
 update: [
  set: [
    snapshots:
      fragment(
        "json_insert(?,?,?)",
        fragment(
          "CASE WHEN ? THEN ? ELSE ? END",
          fragment("json_array_length(?)", p0.snapshots) >= 10,
          fragment("json_remove(?,?)", p0.snapshots, "$[0]"),
          p0.snapshots
        ),
        "$[#]",
        fragment("json_object(?,?,?,?)", "placeables", q1.json, "links", q2.json)
      )
  ]
]>

UPDATE "qwer_projects" AS q0 
SET "snapshots" = json_insert(CASE WHEN json_array_length(q0."snapshots") >= 10 THEN json_remove(q0."snapshots",'$[0]') ELSE q0."snapshots" END,'$[#]',json_object('placeables',s1."json",'links',s2."json")) 
FROM 
    (
        SELECT json_group_array(json_object([...fields])) AS "json" 
        FROM "qwer_placeables" AS sq0 
        WHERE (sq0."project_id" = ?) 
        GROUP BY TRUE
    ) AS s1, 
    (
        SELECT json_group_array(json_object([...fields])) AS "json" 
        FROM "qwer_links" AS sq0 
        WHERE (sq0."project_id" = ?) 
        GROUP BY TRUE
    ) AS s2 
    WHERE (q0."id" = ?)

Expected behavior

The join semantics are retained.

This could be a bug in the sqlite adapter as well, but it's hard to judge from the outside.

[josevalim]

Can you please file this in ecto_sqlite? For Postgres/MySQL/etc we literally generate a LEFT JOIN, so I don't believe the issue is ecto_sql itself but further transformations:

test "update all with left join" do
    query =
      from(m in Schema,
        join: x in assoc(m, :comments),
        left_join: p in assoc(m, :permalink),
        update: [set: [w: m.list2]]
      )
      |> plan(:update_all)

    assert update_all(query) ==
             ~s{UPDATE "schema" AS s0 SET "w" = s0."list2" FROM "schema2" AS s1 LEFT OUTER JOIN "schema3" AS s2 ON s2."id" = s0."y" WHERE (s1."z" = s0."x")}
  end

Unfortunately we cannot transfer issues across orgs.