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@rwilcox
Last active February 27, 2023 17:17
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Spanner and Typescript
// 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!")
})
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