docs: update Sequelize tests and sample (#1949)

* docs: update Sequelize tests and sample

* chore: fix test cases

* fix: show dates as dates

samples/nodejs/sequelize/README.md

@@ -2,7 +2,7 @@
 
 # PGAdapter Spanner and Sequelize
 
-PGAdapter has experimental support for [Sequelize](https://sequelize.org/) with the standard Node.js
+PGAdapter can be used with [Sequelize](https://sequelize.org/) with the standard Node.js
 `pg` driver. This sample application shows how to connect to PGAdapter with Sequelize, and how to
 execute queries and transactions on Cloud Spanner.
 
@@ -15,3 +15,34 @@ npm start
 
 PGAdapter and the emulator are started in a Docker test container by the sample application.
 Docker is therefore required to be installed on your system to run this sample.
+
+## Performance Considerations
+
+### Query Parameters
+
+[Sequelize](https://sequelize.org/) does not use parameterized queries by default. The following query __will not use
+a parameterized query__, which will incur a performance penalty on Spanner.
+
+```typescript
+  // DO NOT USE!
+  const singers = await Singer.findAll({
+    where: {
+      lastName: {[Op.like]: pattern },
+    },
+  });
+```
+
+Instead, construct queries with bind parameters like this:
+
+```typescript
+  // BEST PRACTICE: USE BIND PARAMETERS
+  const singers = await Singer.findAll({
+  where: {
+    lastName: {[Op.like]: literal('$pattern') },
+  },
+  bind: {pattern},
+});
+```
+
+See https://sequelize.org/docs/v6/core-concepts/raw-queries/#bind-parameter for more information on
+bind parameters in Sequelize.

samples/nodejs/sequelize/src/index.ts

@@ -14,7 +14,7 @@
 
 import {createDataModel, startPGAdapter} from './init'
 import {Album, Concert, initModels, Singer, TicketSale, Track, Venue} from '../models/models';
-import {QueryTypes, Sequelize} from "sequelize";
+import {literal, Op, QueryTypes, Sequelize} from "sequelize";
 import {randomInt} from "crypto";
 import {randomAlbumTitle, randomFirstName, randomLastName, randomTrackTitle} from "./random";
 
@@ -60,6 +60,8 @@ async function main() {
   // Create and then print some random data.
   await createRandomSingersAndAlbums(sequelize, 20);
   await printSingersAlbums();
+  // Print all singers whose name start with an 'C'.
+  await printSingersWithLastNameLike('C%');
 
   // Create Venues and Concerts rows.
   // The "venues" table contains a JSONB column.
@@ -142,6 +144,33 @@ async function printSingersAlbums() {
   }
 }
 
+// Selects all Singers whose last name match the given pattern.
+async function printSingersWithLastNameLike(pattern: string) {
+  // Use `literal('$param_name')` in combination with an array of bind parameters
+  // to use parameterized queries on Spanner. This will reduce latency, as Spanner
+  // can cache the execution plan for the query.
+  // See https://sequelize.org/docs/v6/core-concepts/raw-queries/#bind-parameter for
+  // more information on bind parameters in Sequelize.
+  const singers = await Singer.findAll({
+    where: {
+      lastName: {[Op.like]: literal('$pattern') },
+    },
+    bind: {pattern},
+  });
+  console.log(`Found singers whose last name match the pattern ${pattern}:`);
+  for (const singer of singers) {
+    console.log(`Singer ${singer.fullName}`);
+  }
+
+  // This gives the same result, but is inefficient.
+  // DO NOT USE!
+  // const singers = await Singer.findAll({
+  //   where: {
+  //     lastName: {[Op.like]: pattern },
+  //   },
+  // });
+}
+
 // Shows how to execute a stale read on Spanner.
 async function staleRead(sequelize: Sequelize) {
   console.log("");