feat: query ancestors of a query

Author: fahchen

lib/query/ancestors.ex

@@ -7,6 +7,25 @@ defmodule Hierarch.Query.Ancestors do
 
     * `:with_self` - when true to include itself. Defaults to false.
   """
+  def query(%{from: %{source: {_table_name, schema}}} = queryable) do
+    path_column = schema.__hierarch__(:path_column)
+
+    [pk_column] = schema.__schema__(:primary_key)
+
+    uuids_query =
+      from t in queryable,
+      select: %{__uuid__: fragment("regexp_split_to_table(replace(ltree2text(?), '_', '-'), '\\.')", field(t, ^path_column))}
+
+    uuids_array_query =
+      from t in subquery(uuids_query),
+      where: not is_nil(t.__uuid__),
+      or_where: t.__uuid__ != ^"",
+      select: %{__uuids__: fragment("array_agg(cast(? as uuid))", t.__uuid__)}
+
+    schema
+    |> join(:cross, [], a in subquery(uuids_array_query))
+    |> where([t, a], field(t, ^pk_column) in a.__uuids__)
+  end
   def query(%schema{} = struct, opts \\ []) do
     with_self = Keyword.get(opts, :with_self, false)
 

test/hierarch/ancestors_test.exs

@@ -54,4 +54,29 @@ defmodule Hierarch.AncestorsTest do
       assert ancestors == [top]
     end
   end
+
+  describe "ancestors/1" do
+    import Ecto.Query
+
+    test "returns ancestors of a query", catelogs do
+      science  = Map.get(catelogs, "Top.Science")
+      hobbies  = Map.get(catelogs, "Top.Hobbies")
+      pictures = Map.get(catelogs, "Top.Collections.Pictures")
+
+      top         = Map.get(catelogs, "Top")
+      collections = Map.get(catelogs, "Top.Collections")
+
+      query = from(
+        c in Catelog,
+        where: c.id in ^[science.id, hobbies.id, pictures.id]
+      )
+
+      descendants =
+        query
+        |> Hierarch.Query.Ancestors.query()
+        |> Repo.all
+
+      assert_match descendants, [top, collections]
+    end
+  end
 end