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feat: support offset option in relationship joins #214

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feat: support offset option in relationship joins #214

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35 changes: 30 additions & 5 deletions lib/join.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -349,7 +349,8 @@
has_parent_expr? =
opts[:require_lateral?] ||
!!query.__ash_bindings__.context[:data_layer][:has_parent_expr?] ||
not is_nil(query.limit)
not is_nil(query.limit) ||
not is_nil(query.offset)

query =
if has_parent_expr? do
Expand Down Expand Up @@ -457,6 +458,13 @@
|> Ash.Query.unset(:sort)
end
end)
|> then(fn query ->
if not is_nil(Map.get(relationship, :offset)) do

Check warning on line 462 in lib/join.ex

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GitHub Actions / ash-ci / mix credo --strict 

Avoid negated conditions in if-else blocks.
Ash.Query.offset(query, relationship.offset)
else
query
end
end)
|> set_has_parent_expr_context(relationship)
|> case do
%{valid?: true} = related_query ->
Expand Down Expand Up @@ -544,14 +552,23 @@

defp limit_from_many(
query,
%{from_many?: true, destination: destination},
%{from_many?: true, destination: destination} = relationship,
filter,
filter_subquery?,
opts
) do
offset = Map.get(relationship, :offset)

if filter_subquery? do
inner_query =
if offset do
from(row in query, limit: 1, offset: ^offset)
else
from(row in query, limit: 1)
end

query =
from(row in Ecto.Query.subquery(from(row in query, limit: 1)),
from(row in Ecto.Query.subquery(inner_query),
as: ^query.__ash_bindings__.root_binding
)
|> Map.put(:__ash_bindings__, query.__ash_bindings__)
Expand All @@ -578,7 +595,7 @@

defp limit_from_many(
query,
%{limit: limit, destination: destination},
%{limit: limit, destination: destination} = relationship,
filter,
filter_subquery?,
opts
Expand All @@ -587,11 +604,19 @@
# Check if query has parent expressions - if so, we can't wrap in a non-lateral subquery
# because parent references won't resolve across the subquery boundary
has_parent_expr? = !!query.__ash_bindings__.context[:data_layer][:has_parent_expr?]
offset = Map.get(relationship, :offset)

if filter_subquery? && !has_parent_expr? do
# Wrap the limited query in a subquery, then apply filter on top
inner_query =
if offset do
from(row in query, limit: ^limit, offset: ^offset)
else
from(row in query, limit: ^limit)
end

query =
from(row in Ecto.Query.subquery(from(row in query, limit: ^limit)),
from(row in Ecto.Query.subquery(inner_query),
as: ^query.__ash_bindings__.root_binding
)
|> Map.put(:__ash_bindings__, query.__ash_bindings__)
Expand Down
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