relations: walk down the hall
The same data, loaded with relations: { posts: true }, first by findOne and then by find.
main.ts
import { Entity, PrimaryGeneratedColumn, Column, OneToMany, ManyToOne, JoinColumn } from "typeorm";import { connect } from "./db"; @Entity()class User { @PrimaryGeneratedColumn() id!: number; @Column() name!: string; @OneToMany(() => Post, (p) => p.author) posts!: Post[];} @Entity()class Post { @PrimaryGeneratedColumn() id!: number; @Column() title!: string; @Column() authorId!: number; @ManyToOne(() => User, (u) => u.posts) @JoinColumn({ name: "authorId" }) author!: User;} async function main() { const db = await connect([User, Post]); const users = db.getRepository(User); const posts = db.getRepository(Post); await users.insert({ name: "Ann" }); await posts.insert({ title: "Hi", authorId: 1 }); const ann = await users.findOne({ where: { id: 1 }, relations: { posts: true } }); console.log("findOne posts: " + ann!.posts.length); const all = await users.find({ relations: { posts: true } }); console.log("find posts: " + all[0].posts.length);}main();db.ts 38 lines
import "reflect-metadata";import { DataSource } from "typeorm"; let show = false; /** One short line per statement: the verb and the table, enough to count what a call costs. */function short(sql: string): string { const s = sql.replace(/\s+/g, " ").trim(); if (/last_insert_rowid/i.test(s)) return "SELECT new id"; if (/^SELECT DISTINCT "distinctAlias"/i.test(s)) return "SELECT ids (paging)"; const verb = (s.match(/^(SELECT|INSERT INTO|UPDATE|DELETE FROM|BEGIN TRANSACTION|COMMIT|ROLLBACK)/i)?.[0] ?? s.split(" ")[0]).toUpperCase(); const table = s.match(/(?:FROM|INTO|UPDATE)\s+"(\w+)"/i)?.[1]; return table ? verb + " " + table + (/ JOIN /i.test(s) ? " JOIN" : "") : verb;} /** An in-memory SQLite database that prints one line for every SQL statement it runs. */export async function connect(entities: Function[]): Promise<DataSource> { const db = new DataSource({ type: "sqljs", entities, synchronize: true, logging: true, logger: { logQuery: (q: string) => { if (show) console.log("SQL " + short(q)); }, logQueryError: () => {}, logQuerySlow: () => {}, logSchemaBuild: () => {}, logMigration: () => {}, log: () => {}, }, }); await db.initialize(); show = true; return db;} 1. Predict the output
Tap the lines in the order you think they print.
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