fingerprint64 results inconsistent with Google BigQuery

Google BigQuery has farm_fingerprint 64 as a built in function. https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#farm_fingerprint

BiqQuery:

SELECT FARM_FINGERPRINT("1footrue");

Returns -1541654101129638711

lovell/farmhash:

farmhash.fingerprint64("1footrue")

yields 16905089972579912905

Shouldn’t they produce the same? For any string that BQ produces a positive hash for i.e. “2applefalse” both this package and bigquery converge on 2794438866806483259.

[jakelowen]

This also works, no?

const fingerprint64signed = input => {
  return BigInt.asIntN(64, farmhash.fingerprint64(input)).toString();
};

fingerprint64signed("1footrue") yields “-1541654101129638711”

[kechan]

Thanks @lovell - your analysis makes sense. Feel free to close the issue since it seems to be an issue on BQ side and not your library.

On that note: can you think of a helper function that would take the result of your farmhash.fingerprint64 and transform in the same way that BQ does? In essence to recreate their error reliably?

Thanks for clarification on this int type issue. I was taken by surprise as well.

import numpy as np
np.uint64(farmhash.fingerprint64(x)).astype('int64')

then it will give the same result as BigQuery on ‘x’