@torbjornvatn torbjornvatn, Senior Platform Engineer
How do you make sense of all those terabytes of data stuck in your BigQuery database?

Here’s what we tested

We here at Unacast sit on loads of data in several BigQuery databases and have tried several ways of visualizing that data to better understand them. These efforts have been mostly custom Javascript code as a part of our admin UI, but when we read about Re:dash we were eager to test how advanced visualizations we could do with an “off the shelf” solution like that. We wanted both charts showing all kinds of numerical statistics retrieved from that data and maps showing us geographical patterns. Re:dash supports this right out of the box, so what were we waiting for?

Getting up and running

Since we run all our systems on Google Cloud we were really happy to discover that Re:dash offers a pre-built image for Google Compute Engine, and they even have one with BigQuery capabilities preconfigured. This means that when we fire up Re:dash in one of our Google Cloud projects, the BigQuery databases in the same project are automatically available as a data sources ready to be queried. Awesomeness!!

Apart from booting the GCE image itself we had to open some firewall ports (80/443) using the gcloud compute firewall-rules create command, add a certificate to the nginx instance running inside the Re:dash image to enable https and lastly add a dns record for easy access.

The final touch was to add authentication using Google Apps so we could log in using our Unacast Google accounts. This also makes access and user control a breeze.

The power of queries

As the name implies, the power of BigQuery lies in queries on big datasets. To write these queries we can (luckily) just use our old friend SQL so we don’t have to learn some new weird query language. The documentation is nothing less than excellent. There’s a detailed section on Query Syntax and then there’s a really extensive list of Functions that spans from simple COUNT() and SUM() via REGEXP_EXTRACT() on Strings and all kinds of Date manipulations like DATE_DIFF(). There’s also beta support for standard SQL syntax

which is compliant with the SQL 2011 standard and has extensions that support querying nested and repeated data

but that’s sadly not supported in Re:dash yet (at least not in the version included in the GCE image we use).

In Re:dash you can utilize all of BigQuery’s querying power and you can (and should) save those queries with descriptive names to use later for visualizations in dashboards. Here’s a screenshot of the query editor and the observant reader will notice that I’ve used Google’s public nyc-tlc:yellow dataset in this example. It’s a dataset containing lots and lots of data about NYC Yellow Cab trips and I’ll use them in my examples because they’re kind of similar to our beacon interaction data as they contain lat/long coordinates and timestamps for when the interaction occurred.

1000 cab trips

It’s, however, worth noting that you don’t get any autocomplete functionality in Re:dash, so if you want to explore the different functions of BigQuery using the tab key you should use the “native” query editor instead. Just ⌘-C/⌘-V the finished query into Re:dash and start visualizing.

Visualize it

Every query view in Re:dash has a section at the bottom where you can create visualizations of the data returned by that specific query. We can choose between these visualization types: [Boxplot, Chart, Cohort, Counter, Map] and here’s how 100 cab trips look in a map

100 cab trips

When you get a handful of these charts and maps you might want to gather them in a dashboard to e.g. showcase them on a monitor in the office. Re:dash has a dashboard generator where you can choose to add widgets based on the visualizations you have made from your different queries. You can even rename and rearrange these widgets to create the most informative view. Here’s an example dashboard with the map we saw earlier and a graph showing the number of trips for each day in a month. The graph makes it easy to see that the traffic fluctuates throughout the week, with a peak on Fridays.

dashboard

So what’s the conclusion?

Re:dash has been a pleasant experience so far, and it has helped us get more insight into the vast amount of data we have. We discover new ways to query the data because it’s easier to picture a specific graph or map that we want to produce rather than just numbers in columns. We intend to use this as an internal tool to quickly generate visualizations and dashboards of specific datasets to better understand how they relate too and differs from other datasets we have.

There are some rough edges, however, that have been bothering us a bit. The prebuilt GCE images aren’t entirely up to date with the latest releases, unfortunately. The documentation mentions a way to upgrade to the newest release, but we haven’t gotten around to that yet. The lack of support for standard SQL syntax in BigQuery is also a little disappointing since that syntax has even better documentation and the feature set seems larger, but it’s not that big of a deal. The biggest problem we have been facing is that the UI sometimes freezes and crashes that tab in the browser. We haven’t pinpointed exactly what causes it yet, whether it’s the size of the result set or the size of the dataset we’re querying. It’s really annoying regardless of the cause because it’s hard to predict which queries will cause Re:dash to crash. Hopefully, this will be solved when we figure out how to upgrade to a newer version or the Re:dash team releases an updated image.

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Published on March 02, 2017