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Working with BigInts

Arrow supports big integers.

If the JavaScript platform supports the recently introduced BigInt64Array typed array, Arrow JS will use this type.

For convenience ArrowJS inject additional methods (on the object instance) that lets it be converted to JSON, strings, values and primitives

  • bigIntArray.toJSON()
  • bigIntArray.toString()
  • bigIntArray.valueOf()
  • bigIntArray[Symbol.toPrimitive](hint: 'string' | 'number' | 'default')

Notes about Conversion Methods

When you have one of the wide numeric types (Int64, Uint64, or Decimal which is 128bit), those Vector instances always return/accept subarray slices of the underlying 32bit typed arrays.

But to make life easier for people consuming the typed arrays, the Arrow JS API adds some extra methods to the typed arrays before they're returned. The goal of these methods is to handle conversion to and from the various primitive types (number, string, bigint, and JSON.stringify()) so people usually "fall into the pit of success".

One of the added methods is an implementation of [Symbol.toPrimitive], which JS will use when doing certain kinds of implicit primitive coercion.

The implementation of these methods is bifurcated, so if you're in an environment with BigInt support we use the native type, but if not, we'll make a best-effort attempt to return something meaningful (usually the unsigned decimal representation of the number as a string, though we'd appreciate help if someone knows how to compute the signed decimal representation).

Examples:

import { Int64Vector } from 'apache-arrow';
import assert from 'assert';

const bigIntArr = new BigInt64Array([ 1n + BigInt(Number.MAX_SAFE_INTEGER) ])
const lilIntArr = new Int32Array(bigIntArr.buffer)
assert(bigIntArr.length === 1)
assert(lilIntArr.length === 2)

const bigIntVec = Int64Vector.from(bigIntArr)
assert(bigIntVec.length === 1)

const bigIntVal = bigIntVec.get(0)
assert(bigIntVal instanceof Int32Array)
assert(bigIntVal[0] === 0)
assert(bigIntVal[1] === 2097152)

// these implicitly call bigIntVal[Symbol.toPrimitive]()
assert(('' + bigIntVal) == '9007199254740992') // aka bigIntVal[Symbol.toPrimitive]('string')
assert((0 + bigIntVal) == 9007199254740992) // aka bigIntVal[Symbol.toPrimitive]('number')
assert((0n + bigIntVal) == 9007199254740992n) // aka bigIntVal[Symbol.toPrimitive]('default')```