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Fix preloader validation for multiple combinations #4762

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Merged
josevalim merged 1 commit into from
Jul 23, 2026
+6 −1
Merged

Fix preloader validation for multiple combinations #4762

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2 changes: 1 addition & 1 deletion lib/ecto/repo/preloader.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -392,7 +392,7 @@ defmodule Ecto.Repo.Preloader do
# If we are returning many results, we must sort by the key too
query =
case {card, query.combinations} do
{:many, [{kind, _} | []]} ->
{:many, [{kind, _} | _]} ->
raise ArgumentError,
"`#{kind}` queries must be wrapped inside of a subquery " <>
"when preloading a `has_many` or `many_to_many` association. " <>
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5 changes: 5 additions & 0 deletions test/ecto/repo_test.exs
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Expand Up @@ -2138,6 +2138,11 @@ defmodule Ecto.RepoTest do
TestRepo.preload(%MySchema{id: 1}, children: union(query, ^query))
end

assert_raise ArgumentError, msg, fn ->
combination_query = query |> union(^query) |> union(^query)
TestRepo.preload(%MySchema{id: 1}, children: combination_query)
end

msg = ~r"`union_all` queries must be wrapped inside of a subquery"

assert_raise ArgumentError, msg, fn ->
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