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103 lines
2.3 KiB
Go
103 lines
2.3 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/examples/o2mrecur/ent"
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"entgo.io/ent/examples/o2mrecur/ent/node"
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_ "github.com/mattn/go-sqlite3"
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)
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func Example_o2mRecur() {
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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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if err := Do(ctx, client); err != nil {
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log.Fatal(err)
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}
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// Output:
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// Tree leafs [1 3 5]
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// [1 3 5]
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// Node(id=1, value=2, parent_id=0)
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}
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func Do(ctx context.Context, client *ent.Client) error {
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root, err := client.Node.
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Create().
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SetValue(2).
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Save(ctx)
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if err != nil {
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return fmt.Errorf("creating the root: %w", err)
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}
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// Add additional nodes to the tree:
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//
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// 2
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// / \
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// 1 4
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// / \
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// 3 5
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//
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// Unlike `Save`, `SaveX` panics if an error occurs.
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n1 := client.Node.
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Create().
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SetValue(1).
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SetParent(root).
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SaveX(ctx)
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n4 := client.Node.
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Create().
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SetValue(4).
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SetParent(root).
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SaveX(ctx)
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n3 := client.Node.
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Create().
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SetValue(3).
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SetParent(n4).
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SaveX(ctx)
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n5 := client.Node.
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Create().
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SetValue(5).
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SetParent(n4).
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SaveX(ctx)
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fmt.Println("Tree leafs", []int{n1.Value, n3.Value, n5.Value})
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// Output: Tree leafs [1 3 5]
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// Get all leafs (nodes without children).
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// Unlike `Int`, `IntX` panics if an error occurs.
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ints := client.Node.
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Query(). // All nodes.
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Where(node.Not(node.HasChildren())). // Only leafs.
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Order(ent.Asc(node.FieldValue)). // Order by their `value` field.
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GroupBy(node.FieldValue). // Extract only the `value` field.
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IntsX(ctx)
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fmt.Println(ints)
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// Output: [1 3 5]
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// Get orphan nodes (nodes without parent).
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// Unlike `Only`, `OnlyX` panics if an error occurs.
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orphan := client.Node.
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Query().
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Where(node.Not(node.HasParent())).
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OnlyX(ctx)
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fmt.Println(orphan)
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// Output: Node(id=1, value=2, parent_id=0)
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return nil
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}
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