Spanner and Typescript

spanner_client.ts

// I should probably write a blog post about this, but whatever

import { Spanner, Instance } from '@google-cloud/spanner'

import type { Database } from '@google-cloud/spanner'

/**
  Authentication is provided by the local machine user running
  `gcloud auth application-default login`
*/
let gSpannerInstance: (Instance | null) = null
export function getSpannerInstance(instance: string): Instance {
   if (gSpannerInstance) { return gSpannerInstance! }

    const projectId = 'EXAMPLE_PROJECT';
    const instanceId = instance

    // Creates a client
    const spanner = new Spanner({
      projectId: projectId,
    });

    // Gets a reference to a Cloud Spanner instance
    gSpannerInstance = spanner.instance(instanceId);
    return gSpannerInstance!
}


let gSpannerDatabaseInstance: (Database | null) = null
export function getSpannerDatabaseInstance(spannerInstance: Instance, databaseId: string): Database {
  if (gSpannerDatabaseInstance) { return gSpannerDatabaseInstance! }

  gSpannerDatabaseInstance = spannerInstance.database(databaseId);
  return gSpannerDatabaseInstance!
}

class MyResult {
  first_name: string | null
  last_name: string | null

  constructor() {
      this.first_name = null
      this.last_name = null
  }
}

async function main() {
    const db = getSpannerDatabaseInstance( getSpannerInstance('my-instance'),
                                           'my-database' )

    // The query to execute
    const query = {
      sql: 'SELECT first_name, last_name from users',
    };

    // Execute a simple SQL statement
    const [rows] = await db.run(query);
    rows.forEach( (row ) => {
        // row is a Database.PartialResult, but I can't type this variable with
        // this here.
        // HOWEVER, row  is an array of name/value objects, each
        // field you request gets its own object
        // so if you have a first_name field in your table
        // and you select first_name from myTable
        // you will get [ { name: 'first_name', value: 'ryan' }]
        // BUT calling toJSON will get you a plain ol' Javascript object
        // that you would expect
        // { "first_name": "Ryan" }

        let result = row.toJSON() as MyResult  // Teccchnically this is just hope at the compiler level...
        console.log(result)
    });
}

main().then( () => {
  console.log("done!")
})