Reducing model size in Power BI - Dashboard Guide

Dashboard Mode - Reducing model size

Business Question

How can we reduce the size of our Power BI data model to improve performance and save storage?

Sample Data

OrderID	Product	Category	Quantity	Price	OrderDate
1001	Notebook	Stationery	10	2.5	2024-01-10
1002	Pen	Stationery	20	1.2	2024-01-11
1003	Chair	Furniture	5	45	2024-01-12
1004	Desk	Furniture	2	120	2024-01-13
1005	Marker	Stationery	15	3	2024-01-14
1006	Lamp	Furniture	3	30	2024-01-15

Dashboard Components

• KPI Card: Total Sales
  Formula: Total Sales = SUMX(Sales, Sales[Quantity] * Sales[Price])
  Shows total revenue from all sales.
• Table: Sales Data
  Shows raw sales data with columns OrderID, Product, Category, Quantity, Price, OrderDate.
• Bar Chart: Sales by Category
  Formula: Sales by Category = SUMX(Sales, Sales[Quantity] * Sales[Price])
  Shows total sales grouped by product category.
• Measure: Distinct Products Count
  Formula: Distinct Products = DISTINCTCOUNT(Sales[Product])
  Counts unique products sold.
• Measure: Model Size Reduction Tips
  Text box listing tips:
  • Remove unused columns
  • Use numeric data types instead of text where possible
  • Aggregate data before loading
  • Disable auto date/time if not needed

Dashboard Layout

+----------------------+-----------------------+
|      Total Sales      | Distinct Products      |
|       (KPI Card)      |       (KPI Card)       |
+----------------------+-----------------------+
|                                              |
|           Sales by Category (Bar Chart)      |
|                                              |
+----------------------------------------------+
|                                              |
|               Sales Data (Table)              |
|                                              |
+----------------------------------------------+
|                                              |
|          Model Size Reduction Tips (Text)    |
|                                              |
+----------------------------------------------+
  

Interactivity

Adding a slicer for Category will filter the Sales Data table, the Sales by Category bar chart, and update the Total Sales and Distinct Products KPIs accordingly. This helps focus on specific product categories and see how model size reduction tips apply to filtered data.

Self Check

If you add a filter for Category = Furniture, which components update?

• The Total Sales KPI will show sales only for Furniture.
• The Distinct Products KPI will count only Furniture products.
• The Sales by Category bar chart will show only Furniture category data.
• The Sales Data table will list only Furniture sales rows.
• The Model Size Reduction Tips text remains unchanged.

Key Result

Dashboard showing total sales, product counts, sales by category, and tips to reduce Power BI model size.

Practice

1. Which of the following is a simple way to reduce the size of a Power BI data model?

easy

A. Import duplicate tables for safety

B. Add more calculated columns

C. Remove columns that are not used in reports

D. Enable auto date/time for all tables

Solution

1. Step 1: Identify unused data

   Unused columns take up space without adding value to reports.

2. Step 2: Remove unused columns

   Deleting these columns reduces the data model size and improves performance.

3. Final Answer:

   Remove columns that are not used in reports -> Option C

4. Quick Check:

   Removing unused data reduces model size [OK]

Hint: Delete unused columns to shrink model size quickly [OK]

Common Mistakes:

• Keeping all columns regardless of usage
• Adding calculated columns unnecessarily
• Enabling auto date/time increases model size

2. Which syntax correctly disables the auto date/time feature in Power BI using the Options menu?

easy

A. Go to File > Options > Data Load > uncheck 'Auto Date/Time'

B. Use DAX: DISABLE AUTODATE()

C. Right-click table > Disable Auto Date

D. In Power Query, remove date columns

Solution

1. Step 1: Locate auto date/time setting

   It is found under File > Options > Data Load in Power BI Desktop.

2. Step 2: Disable the feature

   Uncheck the 'Auto Date/Time' option to stop Power BI from creating hidden date tables.

3. Final Answer:

   Go to File > Options > Data Load > uncheck 'Auto Date/Time' -> Option A

4. Quick Check:

   Disabling auto date/time reduces hidden data [OK]

Hint: Disable auto date/time in Options to reduce hidden tables [OK]

Common Mistakes:

• Trying to disable auto date/time with DAX
• Removing date columns instead of disabling feature
• Looking for option in Power Query instead of Options menu

3. Given a table with a column 'SalesAmount' stored as Decimal Number, which change reduces model size the most without losing data precision?

medium

A. Keep 'SalesAmount' as Decimal Number

B. Change 'SalesAmount' data type to Whole Number

C. Change 'SalesAmount' data type to Text

D. Change 'SalesAmount' data type to Fixed Decimal Number

Solution

1. Step 1: Understand data types and size

   Decimal Number uses more space; Fixed Decimal Number stores decimals efficiently.

2. Step 2: Choose Fixed Decimal Number

   This type reduces size while keeping decimal precision, unlike Whole Number or Text.

3. Final Answer:

   Change 'SalesAmount' data type to Fixed Decimal Number -> Option D

4. Quick Check:

   Fixed Decimal Number reduces size with decimals [OK]

Hint: Use Fixed Decimal Number for decimals to save space [OK]

Common Mistakes:

• Switching to Whole Number loses decimal data
• Using Text increases model size
• Keeping Decimal Number wastes space

4. You notice your Power BI model size is large. You disabled auto date/time but the size did not reduce. What is the likely cause?

medium

A. You need to refresh the data after disabling auto date/time

B. There are many unused columns still in the model

C. Auto date/time disables only for new reports, not existing ones

D. The model size never changes after disabling features

Solution

1. Step 1: Check for unused columns

   Unused columns consume space even if auto date/time is off.

2. Step 2: Remove unused columns

   Deleting these columns will reduce model size effectively.

3. Final Answer:

   There are many unused columns still in the model -> Option B

4. Quick Check:

   Unused columns keep model large despite disabling features [OK]

Hint: Remove unused columns if disabling features doesn't reduce size [OK]

Common Mistakes:

• Assuming refresh fixes size without removing data
• Thinking auto date/time disables only for new reports
• Believing model size never changes

5. You have a large sales dataset with many columns, including detailed customer info not used in reports. You want to reduce model size and improve report speed. Which combination of actions is best?

hard

A. Remove unused customer columns, disable auto date/time, and change numeric columns to appropriate data types

B. Keep all columns, enable auto date/time, and add calculated columns for analysis

C. Remove only unused columns, keep auto date/time enabled, and leave data types as is

D. Disable auto date/time only, keep all columns and data types unchanged

Solution

1. Step 1: Remove unused columns

   Deleting unused customer info reduces unnecessary data in the model.

2. Step 2: Disable auto date/time

   This stops Power BI from adding hidden date tables that increase size.

3. Step 3: Optimize numeric data types

   Changing numeric columns to smaller or fixed decimal types saves space without losing precision.

4. Final Answer:

   Remove unused customer columns, disable auto date/time, and change numeric columns to appropriate data types -> Option A

5. Quick Check:

   Combining removal, disabling, and data type optimization reduces size best [OK]

Hint: Combine removing unused data, disabling features, and data type tuning [OK]

Common Mistakes:

• Keeping all data and enabling auto date/time
• Only removing columns without disabling features
• Ignoring data type optimization