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