Support materialized CTEs (#466)

Author: maartenvanvliet

lib/ecto/adapters/myxql/connection.ex

@@ -313,7 +313,11 @@ if Code.ensure_loaded?(MyXQL) do
 
     defp cte(%{with_ctes: _}, _), do: []
 
-    defp cte_expr({name, cte}, sources, query) do
+    defp cte_expr({_name, materialized, _cte}, _sources, query) when is_boolean(materialized) do
+      error!(query, "MySQL adapter does not support materialized CTEs")
+    end
+
+    defp cte_expr({name, nil, cte}, sources, query) do
       [quote_name(name), " AS ", cte_query(cte, sources, query)]
     end
 

lib/ecto/adapters/postgres/connection.ex

@@ -409,8 +409,15 @@ if Code.ensure_loaded?(Postgrex) do
 
     defp cte(%{with_ctes: _}, _), do: []
 
-    defp cte_expr({name, cte}, sources, query) do
-      [quote_name(name), " AS ", cte_query(cte, sources, query)]
+    defp cte_expr({name, materialized, cte}, sources, query) do
+      materialized_opt =
+        case materialized do
+          nil -> ""
+          true -> "MATERIALIZED"
+          false -> "NOT MATERIALIZED"  
+        end
+        
+      [quote_name(name), " AS ", materialized_opt, cte_query(cte, sources, query)]
     end
 
     defp cte_query(%Ecto.Query{} = query, sources, parent_query) do

lib/ecto/adapters/tds/connection.ex

@@ -434,7 +434,11 @@ if Code.ensure_loaded?(Tds) do
 
     defp cte(%{with_ctes: _}, _), do: []
 
-    defp cte_expr({name, cte}, sources, query) do
+    defp cte_expr({_name, materialized, _cte}, _sources, query) when is_boolean(materialized) do
+      error!(query, "Tds adapter does not support materialized CTEs")
+    end
+
+    defp cte_expr({name, nil, cte}, sources, query) do
       [quote_name(name), cte_header(cte, query), " AS ", cte_query(cte, sources, query)]
     end
 

mix.lock

@@ -6,7 +6,7 @@
   "decimal": {:hex, :decimal, "2.0.0", "a78296e617b0f5dd4c6caf57c714431347912ffb1d0842e998e9792b5642d697", [:mix], [], "hexpm", "34666e9c55dea81013e77d9d87370fe6cb6291d1ef32f46a1600230b1d44f577"},
   "deep_merge": {:hex, :deep_merge, "0.2.0", "c1050fa2edf4848b9f556fba1b75afc66608a4219659e3311d9c9427b5b680b3", [:mix], [], "hexpm", "e3bf435a54ed27b0ba3a01eb117ae017988804e136edcbe8a6a14c310daa966e"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.29", "149d50dcb3a93d9f3d6f3ecf18c918fb5a2d3c001b5d3305c926cddfbd33355b", [:mix], [], "hexpm", "4902af1b3eb139016aed210888748db8070b8125c2342ce3dcae4f38dcc63503"},
-  "ecto": {:git, "https://github.com/elixir-ecto/ecto.git", "96d4920339d5d645dedaed1ef2ce7428683f529d", []},
+  "ecto": {:git, "https://github.com/elixir-ecto/ecto.git", "954eda40ce768adb0e840a454c843126c9637794", []},
   "ex_doc": {:hex, :ex_doc, "0.29.0", "4a1cb903ce746aceef9c1f9ae8a6c12b742a5461e6959b9d3b24d813ffbea146", [:mix], [{:earmark_parser, "~> 1.4.19", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "f096adb8bbca677d35d278223361c7792d496b3fc0d0224c9d4bc2f651af5db1"},
   "jason": {:hex, :jason, "1.4.0", "e855647bc964a44e2f67df589ccf49105ae039d4179db7f6271dfd3843dc27e6", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "79a3791085b2a0f743ca04cec0f7be26443738779d09302e01318f97bdb82121"},
   "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},

test/ecto/adapters/postgres_test.exs

@@ -156,6 +156,70 @@ defmodule Ecto.Adapters.PostgresTest do
       ~s{INNER JOIN "tree" AS t1 ON t1."id" = s0."category_id"}
   end
 
+  test "materialized CTE" do
+    initial_query =
+      "categories"
+      |> where([c], is_nil(c.parent_id))
+      |> select([c], %{id: c.id, depth: fragment("1")})
+
+    iteration_query =
+      "categories"
+      |> join(:inner, [c], t in "tree", on: t.id == c.parent_id)
+      |> select([c, t], %{id: c.id, depth: fragment("? + 1", t.depth)})
+
+    cte_query = initial_query |> union_all(^iteration_query)
+
+    query =
+      Schema
+      |> recursive_ctes(true)
+      |> with_cte("tree", as: ^cte_query, materialized: true)
+      |> join(:inner, [r], t in "tree", on: t.id == r.category_id)
+      |> select([r, t], %{x: r.x, category_id: t.id, depth: type(t.depth, :integer)})
+      |> plan()
+
+    assert all(query) ==
+      ~s{WITH RECURSIVE "tree" AS MATERIALIZED} <>
+      ~s{(SELECT sc0."id" AS "id", 1 AS "depth" FROM "categories" AS sc0 WHERE (sc0."parent_id" IS NULL) } <>
+      ~s{UNION ALL } <>
+      ~s{(SELECT c0."id", t1."depth" + 1 FROM "categories" AS c0 } <>
+      ~s{INNER JOIN "tree" AS t1 ON t1."id" = c0."parent_id")) } <>
+      ~s{SELECT s0."x", t1."id", t1."depth"::bigint } <>
+      ~s{FROM "schema" AS s0 } <>
+      ~s{INNER JOIN "tree" AS t1 ON t1."id" = s0."category_id"}
+  end
+
+  test "not materialized CTE" do
+    initial_query =
+      "categories"
+      |> where([c], is_nil(c.parent_id))
+      |> select([c], %{id: c.id, depth: fragment("1")})
+
+    iteration_query =
+      "categories"
+      |> join(:inner, [c], t in "tree", on: t.id == c.parent_id)
+      |> select([c, t], %{id: c.id, depth: fragment("? + 1", t.depth)})
+
+    cte_query = initial_query |> union_all(^iteration_query)
+
+    query =
+      Schema
+      |> recursive_ctes(true)
+      |> with_cte("tree", as: ^cte_query, materialized: false)
+      |> join(:inner, [r], t in "tree", on: t.id == r.category_id)
+      |> select([r, t], %{x: r.x, category_id: t.id, depth: type(t.depth, :integer)})
+      |> plan()
+
+    assert all(query) ==
+      ~s{WITH RECURSIVE "tree" AS NOT MATERIALIZED} <>
+      ~s{(SELECT sc0."id" AS "id", 1 AS "depth" FROM "categories" AS sc0 WHERE (sc0."parent_id" IS NULL) } <>
+      ~s{UNION ALL } <>
+      ~s{(SELECT c0."id", t1."depth" + 1 FROM "categories" AS c0 } <>
+      ~s{INNER JOIN "tree" AS t1 ON t1."id" = c0."parent_id")) } <>
+      ~s{SELECT s0."x", t1."id", t1."depth"::bigint } <>
+      ~s{FROM "schema" AS s0 } <>
+      ~s{INNER JOIN "tree" AS t1 ON t1."id" = s0."category_id"}
+  end
+
   @raw_sql_cte """
   SELECT * FROM categories WHERE c.parent_id IS NULL
   UNION ALL