MS Fabric Notebook Spark Reading Data from Semantic Model

[mybarbie9917_LI]

I'm using Fabric notebook to read data from PBI semantic model using Spark.  The above table only has around 180k rows and but it took 45 minutes to retrieve data. 

In the past, it didn't take that long - typically just a few minutes. I'm trying to write this data to a Lakehouse destination and it can never finish the job. This table is one of the smallest and I have other bigger tables to work on. I'm using Fabric capacity. Did MS change something last week or is there anything I can do? 

[Pradeep_O_S]

Which Fabric SKU are you using?

[v-karpurapud]

Hello @mybarbie9917_LI 

I hope this information is helpful. Please let me know if you have any further questions or if you'd like to discuss this further. If this answers your question, please Accept it as a solution and give it a 'Kudos' so others can find it easily.

Thank you.

[v-karpurapud]

Hello @mybarbie9917_LI 

I wanted to check if you had the opportunity to review the information provided. Please feel free to contact us if you have any further questions. If my response has addressed your query, please accept it as a solution and give a 'Kudos' so other members can easily find it.

Thank you.

[BIstvan]

@mybarbie9917_LI  Have you tried running DAX query on Semnatic model.

Try the below. If you have issues on column names tweak in in wrangler.

from pyspark.sql import SparkSession
import sempy.fabric as fabric
import re

# Step 2: Initialize Spark Session (Required for PySpark)
spark = SparkSession.builder.appName("FabricDAXQuery").getOrCreate()

# Ensure the target database exists; create it if it doesn't.
spark.sql("CREATE DATABASE IF NOT EXISTS --- ANYTHING YOU WANT ---")

# Step 3: List available workspaces
df_workspaces = fabric.list_workspaces()

# Convert to PySpark DataFrame and display
df_spark_workspaces = spark.createDataFrame(df_workspaces)
df_spark_workspaces.show(truncate=False) # Display as a Spark DataFrame

# Step 4: List datasets in the specific workspace
workspace_name = "----- WORKSPACE NAME ----" # Change this to your workspace name
df_datasets = fabric.list_datasets(workspace=workspace_name)

# Step 5: Define Dataset and DAX Query
dataset_name = "---- SEMANTIC MODEL NAME -----" # Ensure this matches exactly
dax_string = """

INSERT HERE YOUR DAX QUERY

"""

# Step 6: Run DAX Query with Correct Argument Name
df_dax = fabric.evaluate_dax(
dataset=dataset_name,
dax_string=dax_string, # FIXED: Corrected argument name from `dax_query` to `dax_string`
workspace=workspace_name # Specify the correct workspace
)

# Convert result to PySpark DataFrame
df_spark_dax = spark.createDataFrame(df_dax)

for col_name in df_spark_dax.columns:
match = re.search(r'\[(.*?)\]', col_name)
if match:
# Extract the text within brackets and replace spaces with underscores
new_col_name = match.group(1).replace(" ", "_")
df_spark_dax = df_spark_dax.withColumnRenamed(col_name, new_col_name)

# Step 7: Save DataFrame as a Lakehouse table named 'DAX' under the 'LakeHouse_Sales_Report' database.
df_spark_dax.write.format("delta") \
.mode("overwrite") \
.saveAsTable("----DATABASE NAME ----.----TABLE NAME ----")

[v-karpurapud · Accepted solution]

Hello @mybarbie9917_LI

Thank you @nilendraFabric  for your response!

Thank you for reaching out to the Microsoft Fabric Community. We understand you are experiencing a significant performance drop when querying a Power BI Semantic Model via Spark in Fabric.

This issue could be due to Fabric updates, Spark settings, or inefficient query execution. Since it worked in the past but has slowed down recently, it might be caused by Fabric capacity overload. If many users are running workloads, the capacity can be exhausted, slowing everything down.Could you please try the following methods:

• Microsoft Fabric upgraded to Runtime 1.3 with Apache Spark 3.5, bringing major library updates. If you use custom or overridden libraries, they may cause compatibility issues. Reinstalling libraries is recommended.
  
  Microsoft Fabric January 2025 update | Microsoft Fabric Blog | Microsoft Fabric
  Runtime 1.3 in Fabric - Microsoft Fabric | Microsoft Learn
  Compute management in Fabric environments - Microsoft Fabric | Microsoft Learn

• Optimize Spark settings by adjusting executor cores, memory, and autoscaling. For better performance, try disabling autoscaling and using a fixed number of executors.

• Use monitoring tools like Spark UI to diagnose performance bottlenecks. These tools provide detailed insights into the execution of Spark jobs, helping identify stages that are taking longer than expected.
  Apache Spark monitoring overview - Microsoft Fabric | Microsoft Learn

If the issue persists, it may be helpful to open a support ticket with Microsoft Fabric for further investigation.

How to create a Fabric and Power BI Support ticket - Power BI | Microsoft Learn 

If my response has resolved your query, please mark it as the Accepted Solution to assist others. Additionally, a 'Kudos' would be appreciated if you found my response helpful.

Thank you!

[v-karpurapud]

Hello @mybarbie9917_LI 

May I ask if you have resolved this issue? If so, please mark the helpful reply and accept it as the solution. This will be helpful for other community members who have similar problems to solve it faster.

Thank you.

[nilendraFabric]

Hello @mybarbie9917_LI 

Not sure if something changed but worth trying the query using sempy

from sempy.fabric import FabricDataFrame

d_person = FabricDataFrame.read_table("Semantic Model", "d_person")
d_person = d_person[(d_person.on_leave == 'No') &
(d_person.fte_cw.isin(['FTE', 'CW', 'Other']))]

 `FabricDataFrame` propagates Power BI metadata (relationships, hierarchies) for optimized execution

[mybarbie9917_LI]

Hi @nilendraFabric! Thanks for your recommendation. I tried your codes but FabricDataFrame Class in Fabric doesn't have the method <FabricDataFrame.read_table>.

I also tried the regular <fabric.read_table> to read the whole table but it keeps running for 15 minutes without result.  

import sempy.fabric as fabric
d_person = fabric.read_table(
dataset = "Semantic Model", 
table = "d_person", 
workspace = 'Workspace'
num_rows = 100,
verbose=1)

[nilendraFabric]

Hello @mybarbie9917_LI 

Try with different modes :

df_onelake = FabricDataFrame.read_table(
dataset="YourDatasetName",
table="YourTableName",
mode='onelake',
onelake_import_method='spark'
)