DataStoreReader - Google Cloud Datastore Query Wrapper

DataStoreReader.md

Summary:

• Returns a promise so it's predictable and easier to work with
• Destructuring of entities
• Destructuring of keys
• Destructuring of endCursor (for Pagination support)
• Support for SELECT, FILTER and LIMIT
• Support for ORDER, as replaced with ASCEND and DESCEND for readability
• Queries are chainable of course

const Reader = new DataStoreReader('Inventory');
Reader
  .FILTER('current_amount', '=', '0')
  .LIMIT(5)
  .RUNQUERY()
  .then(()=>{
    // do your magic
  })
  .catch(()=>{
    // do your magic
  });

Files:

• index.js - DataStoreReader setup & class itself
• test.js - Test example

Notes

• Docs is here: https://cloud.google.com/datastore/docs/concepts/queries
• Type checks not included, but easy to add.
• Support for special query types not included, but easy to add: https://cloud.google.com/datastore/docs/concepts/queries#special_query_types

index.js

// Setup
process.env["GOOGLE_APPLICATION_CREDENTIALS"] = __dirname.concat("/google_datastore/XYZ.json");
const GoogleDatastore = require('@google-cloud/datastore');
const Datastore = new GoogleDatastore({
  projectId: 'XYZ'
});

// Class itself
class DataStoreReader{
  constructor (kind, endCursor) {
    let query = Datastore.createQuery(kind);
    if (Boolean(endCursor) === true) {
      query = query.start(endCursor);
    }
    this.query = query;
  }
  ASCEND (a) {
    this.query = this.query.order(a);
    return this;
  }
  DESCEND (a) {
    this.query = this.query.order(a, {
      descending: true,
    });
    return this;
  }
  SELECT (a) {
    this.query = this.query.select(a);
    return this;
  }
  FILTER (a, b, c) {
    this.query = this.query.filter(a, b, c);
    return this;
  }
  LIMIT (a) {
    this.query = this.query.limit(a);
    return this;
  }
  RUNQUERY () {
    return new Promise((resolve, reject)=>{
      Datastore
        .runQuery(this.query)
        .then((results)=>{
          let entities = results[0];
          let keys = entities.map(entity => entity[Datastore.KEY]);
          let info = results[1];
          let endCursor = (
            info.moreResults !== Datastore.NO_MORE_RESULTS ?
            info.endCursor :
            null
          );
          resolve({entities, keys, endCursor});
        })
        .catch(reject);
    });
  }
};

test.js

console.log('TESTING');
const testLoop = (endCursor) => {
  const Reader = new DataStoreReader('XYZ_KIND', endCursor);
  Reader
    // .FILTER('xyz_column_name', '=', '123')
    // .ASCEND('xyz_column_name')
    // .DESCEND('xyz_column_name')
    // .SELECT(['xyz_column_name'])
    // .LIMIT(3)
    .RUNQUERY()
    .then(({entities, keys, endCursor})=>{
      console.log('entities:', entities.length, entities);
      console.log('keys:', keys.length, keys);
      console.log('endCursor:', endCursor);
      if (endCursor) {
        testLoop(endCursor);
      }
    })
    .catch(console.log);
}
testLoop();

Improved @ https://www.npmjs.com/package/google-cloud-datastore-toolkit