How to package a JavaScript library for use in BigQuery
In this article you’ll learn how to package a JavaScript library for use in a BigQuery UDF. We’ll consider a particular example — ethers.js —a complete Ethereum library and wallet implementation in JavaScript. It will allow us to decode raw transactions and logs data in the bigquery-public-data.crypto_ethereum dataset in BigQuery.
The whole process can be broken down into three steps:
- Create a
package.jsfile with the JavaScript lib dependency. - Create
webpack.config.jsand build a JS file using webpack. - Upload the generated JS file to GCS and use it in BigQuery UDF.
You can find the source code for bundling and using ethers.js in this Github repo: https://github.com/blockchain-etl/ethers.js-bigquery.
Now, let’s go through each step in detail.
Create a package.js file
In the image below I highlighted the webpack build script, which we will use later; the dependency on the “ethers” library with its version; and dependencies on webpack and webpack-cli:
Run npm install to download the dependencies.
Create webpack.config.js and build a JS file using webpack
The image below highlights the entry point, starting from which webpack will aggregate all transitive dependencies and assemble them in a single file:
The output configuration tells it to save the result todist/ethers.js file, and that the library will be available as ethers variable when included in a UDF.
Run npm run-script build to generate dist/ethers.js.
Upload the generated JS file to GCS and use it in BigQuery UDF
You’ll need to create a GCS bucket, upload the generated file to it, and make the file publicly readable:
gsutil mb gs://your-bucket
gsutil cp dist/ethers.js gs://your-bucket
gsutil acl ch -u AllUsers:R gs://your-bucket/ethers.jsNow you are ready to use it in a UDF for parsing Ethereum data. The image below highlights the usage of the ethers variable available inside the UDF; how the library is included; and the logs table in the crypto_ethereum dataset:
You can run it by pasting into the BigQuery console query
editor: https://console.cloud.google.com/bigquery. And this is how the result looks like (all CryptoKitties Transfer events):
Also read this article from my fellow D5 member Alex Svanevik on How to get any Ethereum smart contract into BigQuery (in 8 mins).
