🛠️ Power Query Tools Tab in Power BI – Diagnose, Debug & Optimize with Confidence

📌 For: TechTown.in
🧑‍💻 Author: TechTown Team
📅 Updated: June 2025
🔍 Keywords: Power BI Tools Tab, Diagnose Step Power BI, Session Diagnostics, Query Performance Power BI

sample data :

techtown_sales_data Download

🎯 Introduction

Most users think Power Query in Power BI is just for loading and transforming data. But there’s a hidden gem that takes your skills to the next level — the “Tools” tab.

If your queries are slow, nested steps are causing performance issues, or you want to debug your transformations — the Tools tab is your diagnostic command center.

Let’s explore the Tools tab from your screenshot and understand how to use each option for performance tuning and debugging in Power BI.

🔧 Overview of Tools Tab – What You See

These tools help analyze query steps, monitor performance, and understand bottlenecks in your Power BI report.

🧪 1. Diagnose Step

Diagnose Step allows you to monitor and analyze what happens at a specific transformation step in your query.

📌 Use Case:
You’re applying several filters, merges, or calculated columns. Suddenly, performance drops. Use Diagnose Step to:

See how long a step takes to execute
Identify which operation is slowing your query
Evaluate memory or data load at that point

🧠 How to Use:

Select a step in Applied Steps
Click Diagnose Step
Power BI captures the activity and displays a diagnostics table

▶️ 2. Start Diagnostics

Think of this as a “recording” button for Power Query performance.

It tracks all steps, operations, and queries running in the background.

📌 Example: You click “Start Diagnostics” and then refresh your query. Power BI logs:

Time taken for each step
Number of rows read or loaded
Dependencies and execution flow

You can analyze these logs later to optimize slow queries.

⏹️ 3. Stop Diagnostics

Once the diagnostics session is complete, click Stop Diagnostics.

Power Query generates diagnostic result tables, usually:

One for detailed step-wise breakdown
One for summary of queries

📁 These tables appear as new queries in your left panel, so you can analyze them, visualize performance charts, or export.

📌 Tip: Don’t forget to rename them for clarity!

⚙️ 4. Diagnostic Options

This opens a dialog box to customize how diagnostics are recorded.

Options might include:

Whether to include sub-queries
Memory profiling (if supported)
Session-level logging controls

📌 Note: These options may be limited or enhanced depending on your Power BI version and updates.

📊 What Makes These Tools So Valuable?

Feature	Benefit
Diagnose Step	Find bottlenecks in specific steps
Start Diagnostics	Track complete query performance
Stop Diagnostics	Generate analyzable logs as queries
Diagnostic Options	Customize tracking based on needs

📈 Real-Life Scenario – Techtown Sales Data

Imagine you’re loading techtown_sales_data_jan2025 (like in your image), and you notice the query is slow when refreshing.

Solution:

Go to Tools → Start Diagnostics
Refresh the query or apply transformations
Click Stop Diagnostics
Review the generated diagnostic queries

You’ll see step-by-step timings, row counts, and data loading patterns.

From there, you can:

Remove unnecessary columns
Merge queries more efficiently
Use filters before expand/merge steps to reduce data load

💡 Pro Tips for Power Users

Use Diagnose Step when editing complex M code manually
Avoid putting resource-heavy steps (like joins or group by) early in your query
Filter data early to reduce load on following steps
Use diagnostics to decide whether to split large queries into smaller linked queries

✅ Summary

The Tools tab in Power Query isn’t flashy, but it’s crucial for professional-grade Power BI development. If you’re building dashboards for businesses, clients, or even academic projects — understanding what’s happening under the hood is a must.

With just a few clicks, you can:

Monitor performance
Debug logic
Optimize for speed
Produce audit trails

Tools