node.js - Google Datastore combine (union) multiple sets of entity results to achieve OR condition

Question

I am working with NodeJS on Google App Engine with the Datastore database.

Due to the fact that Datastore does not have support the OR operator, I need to run multiple queries and combine the results.

I am planning to run multiple queries and then combine the results into a single array of entity objects. I have a single query working already.

Question: What is a reasonably efficient way to combine two (or more) sets of entities returned by Datastore including de-duplication? I believe this would be a "union" operation in terms of set theory.

Here is the basic query outline that will be run multiple times with some varying filters to achieve the OR conditions required.

  //Set requester username
  const requester = req.user.userName;
  //Create datastore query on Transfer Request kind table
  const task_history = datastore.createQuery('Task');
  //Set query conditions
  task_history.filter('requester', requester);
  //Run datastore query
  datastore.runQuery(task_history, function(err, entities) {
    if(err) {
      console.log('Task History JSON unable to return data results. Error message: ', err);
      return;
      //If query works and returns any entities
    } else if (entities[0]) {
      //Else if query works but does not return any entities return empty JSON response
      res.json(entities); //HOW TO COMBINE (UNION) MULTIPLE SETS OF ENTITIES EFFICIENTLY?
      return;
    }
  });

Here is my original post: Google Datastore filter with OR condition

Answer 1

Waitting for answers