Pagination
If you have millions of records in your database, you wouldn't want to display them all on one page. Doing so would be overwhelming for both the client and the server. That's why pagination is necessary.
Add pagination logic
Tune method parameters in domain/gateway/book_manager.ts:
@@ -5,5 +5,5 @@ export interface BookManager {
updateBook(id: number, b: Book): Promise<void>;
deleteBook(id: number): Promise<void>;
getBook(id: number): Promise<Book | null>;
- getBooks(): Promise<Book[]>;
+ getBooks(offset: number): Promise<Book[]>;
}
Add a parameter named offset for the getBooks method.
Add page_size config item in infrastructure/config/config.ts:
@@ -9,6 +9,7 @@ interface DBConfig {
interface ApplicationConfig {
port: number;
+ page_size: number;
}
export interface CacheConfig {
Setting a value for page_size in config.json:
@@ -1,6 +1,7 @@
{
"app": {
- "port": 3000
+ "port": 3000,
+ "page_size": 5
},
"db": {
"file_name": "test.db",
Wire in page_size in application/wire_helper.ts:
@@ -10,7 +10,7 @@ export class WireHelper {
private kv_store: RedisCache;
constructor(c: Config) {
- this.sql_persistence = new MySQLPersistence(c.db.dsn);
+ this.sql_persistence = new MySQLPersistence(c.db.dsn, c.app.page_size);
this.no_sql_persistence = new MongoPersistence(
c.db.mongo_uri,
c.db.mongo_db_name
Update the query logic to include offset and page_size in infrastructure/database/mysql.ts:
@@ -5,8 +5,10 @@ import { BookManager } from "@/domain/gateway/book_manager";
export class MySQLPersistence implements BookManager {
private db: mysql.Connection;
+ private page_size: number;
- constructor(dsn: string) {
+ constructor(dsn: string, page_size: number) {
+ this.page_size = page_size;
this.db = mysql.createConnection(dsn);
this.db.addListener("error", (err) => {
console.error("Error connecting to MySQL:", err.message);
@@ -67,8 +69,10 @@ export class MySQLPersistence implements BookManager {
return rows.length ? (rows[0] as Book) : null;
}
- async getBooks(): Promise<Book[]> {
- const [rows] = await this.db.promise().query("SELECT * FROM books");
+ async getBooks(offset: number): Promise<Book[]> {
+ const [rows] = await this.db
+ .promise()
+ .query("SELECT * FROM books LIMIT ?, ?", [offset, this.page_size]);
return rows as Book[];
}
Tune cache keys in application/executor/book_operator.ts:
@@ -23,13 +23,14 @@ export class BookOperator {
return await this.bookManager.getBook(id);
}
- async getBooks(): Promise<Book[]> {
- const cache_value = await this.cacheHelper.load(booksKey);
+ async getBooks(offset: number): Promise<Book[]> {
+ const k = `${booksKey}-${offset}`;
+ const cache_value = await this.cacheHelper.load(k);
if (cache_value) {
return JSON.parse(cache_value);
}
- const books = await this.bookManager.getBooks();
- await this.cacheHelper.save(booksKey, JSON.stringify(books));
+ const books = await this.bookManager.getBooks(offset);
+ await this.cacheHelper.save(k, JSON.stringify(books));
return books;
}
Last step, pass in the query parameters in adapter/router.ts:
@@ -16,8 +16,12 @@ class RestHandler {
// Get all books
public async getBooks(req: Request, res: Response): Promise<void> {
+ let offset = parseInt(req.query.o as string);
+ if (isNaN(offset)) {
+ offset = 0;
+ }
try {
- const books = await this.bookOperator.getBooks();
+ const books = await this.bookOperator.getBooks(offset);
res.status(200).json(books);
} catch (err) {
console.error(`Failed to get books: ${err}`);
Alright! Done with code changes. Let's try it out.
Try with curl
Put in some data for test
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Great Gatsby", "author": "F. Scott Fitzgerald", "published_at": "1925-04-10", "description": "A novel depicting the opulent lives of wealthy Long Island residents during the Jazz Age.", "isbn": "9780743273565", "total_pages": 218}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "To Kill a Mockingbird", "author": "Harper Lee", "published_at": "1960-07-11", "description": "A novel set in the American South during the 1930s, dealing with themes of racial injustice and moral growth.", "isbn": "9780061120084", "total_pages": 281}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "1984", "author": "George Orwell", "published_at": "1949-06-08", "description": "A dystopian novel depicting a totalitarian regime, surveillance, and propaganda.", "isbn": "9780451524935", "total_pages": 328}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Pride and Prejudice", "author": "Jane Austen", "published_at": "1813-01-28", "description": "A classic novel exploring the themes of love, reputation, and social class in Georgian England.", "isbn": "9780486284736", "total_pages": 279}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Catcher in the Rye", "author": "J.D. Salinger", "published_at": "1951-07-16", "description": "A novel narrated by a disaffected teenager, exploring themes of alienation and identity.", "isbn": "9780316769488", "total_pages": 277}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Lord of the Rings", "author": "J.R.R. Tolkien", "published_at": "1954-07-29", "description": "A high fantasy epic following the quest to destroy the One Ring and defeat the Dark Lord Sauron.", "isbn": "9780544003415", "total_pages": 1178}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Moby-Dick", "author": "Herman Melville", "published_at": "1851-10-18", "description": "A novel exploring themes of obsession, revenge, and the nature of good and evil.", "isbn": "9780142000083", "total_pages": 624}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Hobbit", "author": "J.R.R. Tolkien", "published_at": "1937-09-21", "description": "A fantasy novel set in Middle-earth, following the adventure of Bilbo Baggins and the quest for treasure.", "isbn": "9780345339683", "total_pages": 310}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Adventures of Huckleberry Finn", "author": "Mark Twain", "published_at": "1884-12-10", "description": "A novel depicting the journey of a young boy and an escaped slave along the Mississippi River.", "isbn": "9780486280615", "total_pages": 366}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "War and Peace", "author": "Leo Tolstoy", "published_at": "1869-01-01", "description": "A novel depicting the Napoleonic era in Russia, exploring themes of love, war, and historical determinism.", "isbn": "9781400079988", "total_pages": 1392}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Alice’s Adventures in Wonderland", "author": "Lewis Carroll", "published_at": "1865-11-26", "description": "A children’s novel featuring a young girl named Alice who falls into a fantastical world populated by peculiar creatures.", "isbn": "9780141439761", "total_pages": 192}' http://localhost:3000/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Odyssey", "author": "Homer", "published_at": "8th Century BC", "description": "An ancient Greek epic poem attributed to Homer, detailing the journey of Odysseus after the Trojan War.", "isbn": "9780140268867", "total_pages": 541}' http://localhost:3000/books
List books of first page
curl -X GET http://localhost:3000/books
Result:
[
{
"id": 2,
"title": "Sample Book 222",
"author": "John Doe",
"published_at": "2023-01-01",
"description": "A sample book description",
"isbn": "1234567890",
"total_pages": 200,
"created_at": "2024-03-01T04:11:57.000Z",
"updated_at": "2024-03-01T04:11:57.000Z"
},
{
"id": 3,
"title": "Sample Book",
"author": "John Doe",
"published_at": "2023-01-01",
"description": "A sample book description",
"isbn": "1234567890",
"total_pages": 200,
"created_at": "2024-03-01T04:40:16.000Z",
"updated_at": "2024-03-01T04:40:16.000Z"
},
{
"id": 4,
"title": "The Great Gatsby",
"author": "F. Scott Fitzgerald",
"published_at": "1925-04-10",
"description": "A novel depicting the opulent lives of wealthy Long Island residents during the Jazz Age.",
"isbn": "9780743273565",
"total_pages": 218,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 5,
"title": "To Kill a Mockingbird",
"author": "Harper Lee",
"published_at": "1960-07-11",
"description": "A novel set in the American South during the 1930s, dealing with themes of racial injustice and moral growth.",
"isbn": "9780061120084",
"total_pages": 281,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 6,
"title": "1984",
"author": "George Orwell",
"published_at": "1949-06-08",
"description": "A dystopian novel depicting a totalitarian regime, surveillance, and propaganda.",
"isbn": "9780451524935",
"total_pages": 328,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
}
]
List books after an offset
curl -X GET "http://localhost:3000/books?o=5"
Result:
[
{
"id": 7,
"title": "Pride and Prejudice",
"author": "Jane Austen",
"published_at": "1813-01-28",
"description": "A classic novel exploring the themes of love, reputation, and social class in Georgian England.",
"isbn": "9780486284736",
"total_pages": 279,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 8,
"title": "The Catcher in the Rye",
"author": "J.D. Salinger",
"published_at": "1951-07-16",
"description": "A novel narrated by a disaffected teenager, exploring themes of alienation and identity.",
"isbn": "9780316769488",
"total_pages": 277,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 9,
"title": "The Lord of the Rings",
"author": "J.R.R. Tolkien",
"published_at": "1954-07-29",
"description": "A high fantasy epic following the quest to destroy the One Ring and defeat the Dark Lord Sauron.",
"isbn": "9780544003415",
"total_pages": 1178,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 10,
"title": "Moby-Dick",
"author": "Herman Melville",
"published_at": "1851-10-18",
"description": "A novel exploring themes of obsession, revenge, and the nature of good and evil.",
"isbn": "9780142000083",
"total_pages": 624,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 11,
"title": "The Hobbit",
"author": "J.R.R. Tolkien",
"published_at": "1937-09-21",
"description": "A fantasy novel set in Middle-earth, following the adventure of Bilbo Baggins and the quest for treasure.",
"isbn": "9780345339683",
"total_pages": 310,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
}
]
List books after another offset
curl -X GET "http://localhost:3000/books?o=10"
Result:
[
{
"id": 12,
"title": "The Adventures of Huckleberry Finn",
"author": "Mark Twain",
"published_at": "1884-12-10",
"description": "A novel depicting the journey of a young boy and an escaped slave along the Mississippi River.",
"isbn": "9780486280615",
"total_pages": 366,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 13,
"title": "War and Peace",
"author": "Leo Tolstoy",
"published_at": "1869-01-01",
"description": "A novel depicting the Napoleonic era in Russia, exploring themes of love, war, and historical determinism.",
"isbn": "9781400079988",
"total_pages": 1392,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 14,
"title": "Alice’s Adventures in Wonderland",
"author": "Lewis Carroll",
"published_at": "1865-11-26",
"description": "A children’s novel featuring a young girl named Alice who falls into a fantastical world populated by peculiar creatures.",
"isbn": "9780141439761",
"total_pages": 192,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
},
{
"id": 15,
"title": "The Odyssey",
"author": "Homer",
"published_at": "8th Century BC",
"description": "An ancient Greek epic poem attributed to Homer, detailing the journey of Odysseus after the Trojan War.",
"isbn": "9780140268867",
"total_pages": 541,
"created_at": "2024-03-01T21:48:25.000Z",
"updated_at": "2024-03-01T21:48:25.000Z"
}
]
Looks like pagination is working! So far so good!
Loading...
> code result goes here