Every read is a trip
Two lookups and a count. Count the SELECTs, and see what a miss gives back.
main.ts
import { Entity, PrimaryGeneratedColumn, Column } from "typeorm";import { connect } from "./db"; @Entity()class User { @PrimaryGeneratedColumn() id!: number; @Column() name!: string;} async function main() { const db = await connect([User]); const users = db.getRepository(User); await users.insert([{ name: "Ann" }, { name: "Bo" }]); const bo = await users.findOneBy({ name: "Bo" }); console.log("found id " + bo!.id); const zed = await users.findOneBy({ name: "Zed" }); console.log("missing: " + zed); const n = await users.count(); console.log(n + " users");}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.
- 1…
- 2…
- 3…
- 4…
- 5…
- 6…
- 7…
- 8…
- 9…