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javascriptnode.jsmongodbmongoosebson
Sawyer
Sawyer

Reputation: 241

How would you store a number larger than the max 64 bit int in mongoDb?

The number is larger than 9223372036854775807 - too big for NumberLong, which is mongo's native 64-bit long type. What's the best way to do this/the best field type?

Is it possible to preserve any of the querying functionality of a smaller integer (such as {$lt})?

The big numbers are being generated by bignumber.js, and I'm using mongoose to interact with mongoDb.

Upvotes: 7

Views: 7268

Answers (2)

Maxime Pacary
Maxime Pacary

Reputation: 23041

Since MongoDB 3.4, it is possible to use NumberDecimal type (also documented as Decimal128 on MongoDB & Mongoose docs) following the IEEE 754 spec.

It has the ability to store maximum and minimum values in the order of 10^6144 and 10^-6143, and supports 34 decimal digits of precision (source).

Tested with Mongoose 6.6:

const mongoose = require('mongoose');

const StatisticsSchema = mongoose.Schema({
    someMetric: { type: mongoose.Types.Decimal128, default: 0 },
    ...
}

Storing a Decimal128 value in DB requires doing:

statistic.someMetric = new mongoose.Types.Decimal128(someNumber.toString());
await statistic.save();

It supports all the MongoDB operators I could test so far ($gt, $lt...) and even aggregation pipelines with operators like $sum.

On the NodeJS side, to overcome Number type limitations (safe integers up to 2^53-1, i.e. ~9 quadrillions), you can use builtin BigInt if you don't need decimals. Overall, the conversions between BigInt (JS side) & Decimal128 (Mongo side) can be cumbersome (e.g. you may have to remove trailing ".0000" from Decimal128 numbers retrieved from DB), however such an approach was definitely a viable option for my use case.

Upvotes: 0

Slava Fomin II
Slava Fomin II

Reputation: 28621

I'm afraid that the only viable/safe option would be to store such big numbers as a string and serialize it back and forth between the application and MongoDB when read/written. However, you will loose the ability to use MongoDB built-in functions that work with numbers (you can still cast the values to numbers, but it won't be safe anymore).

Upvotes: 1

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