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Data Engineering
Join discussions on data engineering best practices, architectures, and optimization strategies within the Databricks Community. Exchange insights and solutions with fellow data engineers.
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Forum Posts

austinoyoung
by • New Contributor III
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  • 2 replies
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Resolved! oracle sequence number

Dear All,I am trying to use jdbc driver to connect to an oracle database and append a new record to a table. The table has a column needs to be populated with a sequence number. I've been trying to use select `<sequence_name>.nextval` to get the sequ...

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Louis_Frolio
Databricks Employee
  • 2 kudos

Hey @austinoyoung ,  Short answer: Don’t try to pull the sequence in your Spark insert. Let Oracle assign it. Why this happens (ORA-02287: sequence number not allowed here Spark’s JDBC writer generates parameterized INSERT statements like: INSERT INT...

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bidek56
by • Contributor
  • 978 Views
  • 1 replies
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Resolved! Stack traces as standard error in job logs

When using DBR 16.4, I am seeing a lot of Stack traces as standard error in jobs, any idea why they are showing up and how to turn then off? Thx"FlagSettingCacheMetricsTimer" id=18 state=WAITING- waiting on <0x2d1573c6> (a java.util.TaskQueue)- locke...

  • 978 Views
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bidek56
Contributor
  • 1 kudos

spark.databricks.driver.disableJvmThreadDump=trueThis setting will remove the ST. 

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saab123
by • New Contributor II
  • 4446 Views
  • 1 replies
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Not able to export maps in dashboards

When we export a dashboard with maps, the map background doesn't show up in the pdf. 

  • 4446 Views
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mark_ott
Databricks Employee
  • 0 kudos

When exporting a Databricks dashboard with maps to PDF, it is a known issue that the map background sometimes does not appear in the exported PDF file. This problem has been discussed in the Databricks community as of early 2025, and appears to be a ...

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SrihariB
by • New Contributor
  • 5802 Views
  • 1 replies
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Read from multiple sources in a single stream

Hey all, I am trying to read data from multiple s3 locations using a single stream DLT pipeline and loading data into a single target. Here is the scenario. S3 Locations: Below are my s3 raw locations with change in the directory names at the end. Ba...

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mark_ott
Databricks Employee
  • 0 kudos

You are using Databricks Autoloader (cloudFiles) within a Delta Live Tables (DLT) pipeline to ingest streaming Parquet data from multiple S3 directories with a wildcard pattern, and you want to ensure all matching directories’ data is included in a s...

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Mauro
by • Databricks Partner
  • 4616 Views
  • 1 replies
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DLT change in hive metastore destination to unity catalog

A change recently came out in which Databricks necessarily requires using the Unity Catalog as the output of a DLT because previously it was HiveMetaStore. At first I was working using CDC plus expectations which resulted in the "allow_expectations_c...

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mark_ott
Databricks Employee
  • 0 kudos

Databricks has recently enforced Unity Catalog as the output target for Delta Live Tables (DLT), replacing the legacy Hive Metastore approach. As a result, the familiar "allow_expectations_col" column, which was automatically added to help track and ...

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Yuppp
by • New Contributor
  • 5866 Views
  • 1 replies
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Need help with setting up ForEach task in Databricks

Hi everyone,I have a workflow involving two notebooks: Notebook A and Notebook B. At the end of Notebook A, we generate a variable number of files, let's call it N. I want to run Notebook B for each of these N files.I know Databricks has a Foreach ta...

For Each.jpg Task.jpg
Data Engineering
ForEach
Workflows
  • 5866 Views
  • 1 replies
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mark_ott
Databricks Employee
  • 0 kudos

You can use Databricks Workflows' foreach task to handle running Notebook B for each file generated in Notebook A. The key is to pass each path as a parameter to Notebook B using Databricks task values and workflows features, not widgets set manually...

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ironv
by • New Contributor
  • 6745 Views
  • 1 replies
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using concurrent.futures for parallelization

Hi, trying to copy a table with billions of rows from an enterprise data source into my databricks table.  To do this, I need to use a homegrown library which handles auth etc, runs the query and return a dataframe.  I am partitioning the table using...

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mark_ott
Databricks Employee
  • 0 kudos

The "SparkSession$ does not exist in the JVM" error in your scenario is almost always due to the use of multiprocessing (like ProcessPoolExecutor) with Spark. Spark contexts and sessions cannot safely be shared across processes, especially in Databri...

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umahesb3
by • New Contributor
  • 6035 Views
  • 1 replies
  • 1 kudos

Facing issues databricks asset bundle, All jobs are getting Deployed into specified targets Instead

Facing issues databricks asset bundle, All jobs are getting Deployed into specified targets Instead of defined target following was files i am using resourser yaml and databricks yml file , i am using Databricks CLI v0.240.0 , i am using databricks b...

  • 6035 Views
  • 1 replies
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mark_ott
Databricks Employee
  • 1 kudos

The issue you’re facing—where all Databricks Asset Bundle jobs are being deployed to all targets instead of only the defined target(s)—appears to be a known limitation in how the bundle resource inclusion and target mapping works in the Databricks CL...

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shubham_007
by • Contributor III
  • 4511 Views
  • 1 replies
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Dear experts, need urgent help on logic.

Dear experts,I am facing difficulty while developing pyspark automation logic on “Developing automation logic to delete/remove display() and cache() method used in scripts in multiple databricks notebooks (tasks)”.kindly advise on developing automati...

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mark_ott
Databricks Employee
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To automate the removal of display() and cache() method calls from multiple PySpark scripts in Databricks notebooks, develop a script that programmatically processes exportable notebook source files (usually in .dbc or .ipynb format) using text-based...

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ADuma
by • New Contributor III
  • 4831 Views
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Strcutured Streaming with queue in separate storage account

Hello,we are running a structured streaming job which consumes zipped Json files that arrive in our Azure Prod storage account. We are using AutoLoader and have set up an Eventgrid Queue which we pass to the streaming job using cloudFiles.queueName. ...

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mark_ott
Databricks Employee
  • 0 kudos

You are attempting to have your Test Databricks streaming job consume files that arrive in your Prod storage, using AutoLoader and EventGrid notifications, without physically copying the data or EventGrid queue to Test. The core challenge is that Eve...

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turagittech
by • Contributor II
  • 5497 Views
  • 1 replies
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Identify source of data in query

Hi All,I have an issue. I have several databases with the same schemas I need to source data from. Those databases are going to end up aggregated in a data warehouse. The problem is the id column in each means different things. Example: a client id i...

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mark_ott
Databricks Employee
  • 0 kudos

Migrating from Data Factory to Databricks for ETL and warehousing is a solid choice, especially for flexibility and cost-effectiveness in data engineering projects. The core issue—disambiguating “id” fields that are only unique within each source dat...

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jeremy98
by • Honored Contributor
  • 9475 Views
  • 2 replies
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Best practice on how to set up a medallion architecture pipelines inside DAB

Hi Community,My team and I are working on refactoring our folder repository structure. Currently, I have been placing pipelines related to the Medallion architecture inside a folder named notebook/. However, I believe they should be moved to src/ sin...

  • 9475 Views
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mark_ott
Databricks Employee
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Refactoring your folder structure and naming conventions for Medallion architecture pipelines is an essential step to keep code maintainable and intuitive. Based on your context, shifting these pipelines from notebook/ to src/ is a solid move, especi...

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MaximeGendre
by • New Contributor III
  • 5124 Views
  • 2 replies
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RLS function : concat vs list

Hello all, I'm designing a function to implement RLS on Unity Catalog for multiple tables of different size (1k to 10G rows).RLS will be applied on two columns and 150+ groups.I wonder what would be more performant :Solution 1: exhaustive (boring) li...

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mark_ott
Databricks Employee
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The more performant solution for Row-Level Security (RLS) in Unity Catalog, when applying to two columns and 150+ groups, generally depends on how much of the access check logic can be pushed into efficient, indexable predicates versus computed at ru...

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kenmyers-8451
by • Contributor II
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Long runtimes on simple copying of data

Hi my team has been trying to identify areas where we can improve our processes. We have some long runtimes on processes that have multiple joins and aggregations. To create a baseline we have been running tests on a simple select and write operation...

kenmyers8451_0-1739400824751.png
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mark_ott
Databricks Employee
  • 0 kudos

Your slow Spark runtime and unexpectedly long WholeStageCodeGen compute times are likely tied to a mix of Delta Lake features (especially deletion vectors), Spark’s physical plan, and partition handling. Here’s a detailed breakdown and advice based o...

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saadi
by • New Contributor
  • 5319 Views
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Resolved! Could not connect Self Hosted MySQL Database in Azure Databricks

Hi,I am trying to connect a self-hosted MySQL database in Databricks but keep encountering errors.Database Setup:The MySQL database is hosted on a VM.We use DBeaver or Navicat to query it.Connection to the database requires an active Azure VPN Client...

  • 5319 Views
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mark_ott
Databricks Employee
  • 0 kudos

To connect a self-hosted MySQL database (on a VM, Azure VPN required) to Databricks, you need several components to align: network access from Databricks to MySQL, proper JDBC connector configuration, and correct authentication. This setup is common ...

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