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User16783853906
by Contributor III
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Metaexception [Version information not found in metastore] during cluster [re]start

Trying to configure new external metastore and running into the following exception during cluster initialization - Caused by: MetaException(message:Version information not found in metastore. )   at org.apache.hadoop.hive.metastore.RetryingHMSHandl...

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User16783853906
Contributor III
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The above exception happens when the hive schema is not available in the metastore instance. Please check in your init scripts to make sure the following flag is enabled to create hive Schema and tables if not already present. datanucleus.autoCreateA...

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User16869510359
by Esteemed Contributor
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User16869510359
Esteemed Contributor
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The below code snippet can be used to get the DBR details on a HC clusterprint("hadoopVersion:" + sc._gateway.jvm.org.apache.hadoop.util.VersionInfo.getVersion()) print("baseVersion:" + sc._gateway.jvm.org.apache.spark.BuildInfo.sparkBranch()) print(...

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aladda
by Honored Contributor II
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User16869510359
Esteemed Contributor
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Databricks notebooks can be exported and stored in S3 or any other object storage. The internal storage of the databricks notebook cannot be changed or configured. The implementation is internal to Databicks control plane and not user configurable.

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User16869510359
by Esteemed Contributor
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User16869510359
Esteemed Contributor
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The below code snippet is useful to get the modification time of files. %scala import scala.util.Try import org.apache.hadoop.conf.Configuration import org.apache.hadoop.fs.{FileSystem, Path} import org.apache.hadoop.io.IOUtils import java.io.IOExcep...

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User16869510359
by Esteemed Contributor
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Resolved! How and when to capture the thread dump of the Spark driver?

What is the best way to capture the thread dump of the Spark driver process. Also, when should I capture the thread dump?

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User16869510359
Esteemed Contributor
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For Spark driver the process is the same. Choose the driver from the Executor page and view the thread dump. A thread dump is the footprints of the JVM they are very useful in debugging issues where the JVM process is stuck or making extremely slow p...

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User16869510359
by Esteemed Contributor
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Resolved! Autoloader: How to identify the backlog in RocksDB

With S3-SQS it was easier to identify the backlog ( the messages that are fetched from SQS and not consumed by the streaming job) How to find the same with Auto-loader

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User16869510359
Esteemed Contributor
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For DBR 8.2 or later, the backlog details are captured in the Streaming metricsEg:

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User16783854657
by New Contributor III
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Resolved! How to ensure that a Databricks Run Submit run invoked from Airflow only runs one time?

I am running jobs on Databricks using the Run Submit API with Airflow. I have noticed that rarely, a particular run is run more than one time at once. Why?

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User16869510359
Esteemed Contributor
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Idempotency can be ensured by providing the idempotency token. It's easy to pass the same through REST API as mentioned in the below doc:https://kb.databricks.com/jobs/jobs-idempotency.htmlThe primary reason for multiple runs is the client submits t...

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User16869510359
by Esteemed Contributor
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Resolved! Performance improvement after running VACUUM commands

How often should I run VACUUM commands? Will running the VACUUM command on a Delta table improve my read/write performance or is it just the storage benefits.

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User16869510359
Esteemed Contributor
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VACUUM removes uncommitted/stale files from the Storage. The primary benefit is to save the storage cost. Ideally running VACUUM should not show any performance improvement as Delta does not list the storage directories but rather access the files di...

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User16869510359
by Esteemed Contributor
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Resolved! Databricks Spark Vs Spark on Yarn

I am moving my Spark workloads from EMR/on-premise Spark cluster to Databricks. I understand Databricks Spark is different from Yarn. How is the Databricks architecture different from yarn?

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User16869510359
Esteemed Contributor
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Users often compare Databricks cluster vs Yarn Cluster. It's not an Apple to Apple comparison. A Databricks cluster should be compared to a Spark Application that is submitted on Yarn. A Spark Application on Yarn will have a driver container and exe...

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User16783854657
by New Contributor III
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Does running OPTIMIZE on a delta table destroy the transaction history of table?

If I run OPTIMIZE on a Delta Lake table, will it prevent me from time travelling to a version before OPTIMIZE was run?

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User16783854657
New Contributor III
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No, you will still be able to time travel to versions previous to the OPTIMIZE command. OPTIMIZE is just another transaction like MERGE, UPDATE, etc. Check out these docs to learn more about retention periods and the VACUUM command.

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User16826987838
by Contributor
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How do I find the users in workspaces

Looking to pull a list of all the users in their workspaces (including the ones who have never done anything), is there a way to do that? This for AWS

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Ryan_Chynoweth
Honored Contributor III
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You can use the SKIM APIs. Endpoint: https://docs.databricks.com/dev-tools/api/latest/scim/scim-users.html#get-users Or you can use the Workspace API. The workspace API does not have a direct list users command, but you can use the workspace API to l...

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User16783853906
by Contributor III
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Resolved! Max Columns for Delta table

Is there an upper limit/recommended max value for no. of columns for Delta table?

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User16783853906
Contributor III
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Original answer posted by @Gray Gwizdz​ This was a fun question to try and find the answer to! Thank you for that I reviewed some of the most recent issues/bugs reported with Delta Lake and was able to find a similar issue where a user was running i...

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User16783853501
by New Contributor II
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Databricks Autoloader Best practice

Databricks Autoloader is a popular mechanism for ingesting data/files from cloud storage into Delta; for a very high throughput source, what are the best practices to be following while scaling up an autoloader based pipeline to the tune of millions ...

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User16783853906
by Contributor III
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Resolved! How to resuse Pandas code in PySpark?

I have single threaded Pandas code that is both not yet supported by Koalas nor easy to reimplement in PySpark. I would like to distribute this workload using Spark without rewriting all my Pandas code - is this possible?

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User16783853906
Contributor III
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This is for a specific scenario where the code is not yet supported by Koalas. One approach to consider is using a Pandas UDF, and splitting up the work in a way that allows your processing to move forward. This notebook is a great example of taking ...

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User16783853906
by Contributor III
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Trigger.once mode recommendation

When is it recommended to use Trigger.once mode compared to fixed processing intervals with micro batches?

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User16869510359
Esteemed Contributor
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Also note, the configurations like maxFilesPerTrigger, maxBytesPerTrigger are ignored with Trigger.Once. Streaming queries with significantly less throughput can switch to Trigger.Once to avoid the continuous execution of the job checking the availab...

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