Today I would like to talk about a simple topic, AL Compiler Diagnostics.
This is a new feature of BC19, but I only found it available on BC19.1 recently.
In the April release of Power BI Desktop the Power Query Query Diagnostics feature was enhanced so that you can now return performance counter data. As the blog post says:
When you run performance counters, every half second Power Query will take a snapshot of resource utilization. This isn’t useful for very fast queries but can be helpful for queries that use up a lot more resources.
Last week’s post showed an M function that took Power Query diagnostics data and formatted in a way that made it suitable for visualisation in a Power BI Decomposition Tree visual. This is great for understanding what’s going on at a high level, but by doing this you also lose a lot of detailed information from the diagnostics logs that could be useful for performance tuning.
Recently I’ve been working with the Power Query team to come up with some ways to help developers understand the data returned by the new Power Query diagnostics functionality. In this, the first of two posts, I’m going to share a Power Query function that reformats diagnostics data in a way that makes it easy to visualise using the Power BI Decomposition Tree visual.
I’ve blogged a few times about the tracing functionality that is built into Power Query/Get&Transform and Power BI (see here and here). The trace files themselves clearly contain a lot of interesting information, but there’s no official documentation about what they contain and the format seems to have changed several times.