如何从bigquery nodejs api获取整数？

Question

I am fetching data from bigquery which I need to store in MongoDB as integer, so that I can perform operations on that data in Mongo. Even though the data types of columns in bigquery is Integer, its nodejs api is returning string in its Javascript object. Eg I'm getting results that look like [{row1:'3',row2:'4',row3:'5'},{row1:'13',row2:'14',row3:'15'}...]

typeof gives string on each element of object. I can run a loop and convert each element to integer, but that is not scalable on the data set. Also, I don't want all strings to be converted to integers, only ones which are stored as integer in bigquery. I'm using gcloud module in nodejs to fetch data.

Answer 1

assuming you know where the type property is on the response, something like this would work.

var response = [{type: 'Integer', value: '13'} /* other objects.. */];

var mappedResponse = response.map(function(item) {
  // Put your logic here
  // This implementation just bails
  if (item.type != 'Integer') return item;

  // This just converts the value to an integer, but beware
  // it returns NaN if the value isn't actually a number
  item.value = parseInt(item.value);
  // you MUST return the item after modifying it.
  return item;      
});

This still loops over each item, but immediately bails out if it's not what we're looking for. Could also compose multiple maps and filters to generalize this out.

The only way to get by this is by first applying a filter, but this basically achieves the same thing as our initial type check

var mappedResponse = response
  // Now we only deal with integers in the map function
  .filter(x => x.type == 'Integer)
  .map(function(item) {
    // This just converts the value to an integer, but beware
    // it returns NaN if the value isn't actually a number
    item.value = parseInt(item.value);
    // you MUST return the item after modifying it.
    return item;      
  });

Answer 2

BigQuery deliberately encodes integers as strings when returning them via API to avoid loss of precision for large values. For now, the only option is to parse them on the client side.