snapshot of https://github.com/ent/ent.git (master, 2026-09-15; blobs > 131072B omitted)

examples/fs/example_test.go

@@ -0,0 +1,97 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"entgo.io/ent/dialect/sql"
+	"entgo.io/ent/examples/fs/ent"
+	"entgo.io/ent/examples/fs/ent/file"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func Example_recursiveTraversal() {
+	client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
+	if err != nil {
+		log.Fatalf("failed opening connection to sqlite: %v", err)
+	}
+	defer client.Close()
+	ctx := context.Background()
+	// Run the auto migration tool.
+	if err := client.Schema.Create(ctx); err != nil {
+		log.Fatalf("failed creating schema resources: %v", err)
+	}
+
+	// Add multiple files in the following tree structure:
+	//
+	//	a/
+	//	├─ b/
+	//	│  ├─ ba
+	//	│  ├─ bb
+	//	│  └─ bc (deleted)
+	//	├─ c/ (deleted)
+	//	│  ├─ ca
+	//	│  └─ cb
+	//	└─ d (deleted)
+	//
+	a := client.File.Create().SetName("a").SaveX(ctx)
+	b := client.File.Create().SetName("b").SetParent(a).SaveX(ctx)
+	client.File.Create().SetName("ba").SetParent(b).SaveX(ctx)
+	client.File.Create().SetName("bb").SetParent(b).SaveX(ctx)
+	client.File.Create().SetName("bc").SetParent(b).SetDeleted(true).SaveX(ctx)
+	c := client.File.Create().SetName("c").SetParent(a).SetDeleted(true).SaveX(ctx)
+	client.File.Create().SetName("ca").SetParent(c).SaveX(ctx)
+	client.File.Create().SetName("cb").SetParent(c).SaveX(ctx)
+	client.File.Create().SetName("d").SetParent(a).SetDeleted(true).SaveX(ctx)
+
+	// Query undeleted files:
+	//
+	//	a/
+	//	└─ b/
+	//	   ├─ ba
+	//	   └─ bb
+	//
+	names := client.File.Query().
+		Where(func(s *sql.Selector) {
+			t1, t2 := sql.Table(file.Table), sql.Table(file.Table)
+			with := sql.WithRecursive("undeleted", file.FieldID, file.FieldParentID)
+			with.As(
+				// The initial `SELECT` statement executed once at the start,
+				// and produces the initial row or rows for the recursion.
+				sql.Select(t1.Columns(file.FieldID, file.FieldParentID)...).
+					From(t1).
+					Where(
+						sql.And(
+							sql.IsNull(t1.C(file.FieldParentID)),
+							sql.EQ(t1.C(file.FieldDeleted), false),
+						),
+					).
+					// Merge the `SELECT` statement above with the following:
+					UnionAll(
+						// A `SELECT` statement that produces additional rows and recurses by referring
+						// to the CTE name (e.g. "undeleted"), and ends when there are no more new rows.
+						sql.Select(t2.Columns(file.FieldID, file.FieldParentID)...).
+							From(t2).
+							Join(with).
+							On(t2.C(file.FieldParentID), with.C(file.FieldID)).
+							Where(
+								sql.EQ(t1.C(file.FieldDeleted), false),
+							),
+					),
+			)
+			// Join the root `SELECT` query with the CTE result (`WITH` clause).
+			s.Prefix(with).Join(with).On(s.C(file.FieldID), with.C(file.FieldID))
+		}).
+		Select(file.FieldName).
+		StringsX(ctx)
+	fmt.Printf("%q\n", names)
+
+	// Output:
+	// ["a" "b" "ba" "bb"]
+}