Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, see the [ blog post ](https://amazonaws-china.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/). 

# Diagnostic queries for query tuning
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Use the following queries to identify issues with queries or underlying tables that can affect query performance. We recommend using these queries with the query tuning processes discussed in [Query analysis and improvement](c-query-tuning.md).

**Note**  
These queries are for Amazon Redshift provisioned clusters. These queries are not for use with Redshift Serverless workgroups.

**Topics**
+ [Identifying queries that are top candidates for tuning](identify-queries-that-are-top-candidates-for-tuning.md)
+ [Identifying tables with data skew or unsorted rows](identify-tables-with-data-skew-or-unsorted-rows.md)
+ [Identifying queries with nested loops](identify-queries-with-nested-loops.md)
+ [Reviewing queue wait times for queries](review-queue-wait-times-for-queries.md)
+ [Reviewing query alerts by table](review-query-alerts-by-table.md)
+ [Identifying tables with missing statistics](identify-tables-with-missing-statistics.md)