Скачать или смотреть Resolving the Postgres Create Index Command Hanging Issue

Having trouble with the `Postgres Create Index` command hanging? This guide explains common reasons for indexing delays and offers practical tips for resolving the issue.
---
This video is based on the question https://stackoverflow.com/q/62533839/ asked by the user 'Rocket04' ( https://stackoverflow.com/u/1012803/ ) and on the answer https://stackoverflow.com/a/62534858/ provided by the user 'Laurenz Albe' ( https://stackoverflow.com/u/6464308/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Postgres Create Index command hangs

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving the Postgres Create Index Command Hanging Issue: A Step-by-Step Guide

Introduction

If you're working with large datasets in PostgreSQL, you may encounter a frustrating issue: the CREATE INDEX command hanging indefinitely. This problem can arise during the creation of an index on a massive table, and it can leave you wondering what went wrong and how to fix it. In this guide, we'll explore the nature of this issue and provide a structured solution to help you get back on track.

Understanding the Problem

When you attempt to create an index on a table with billions of rows, various factors can lead to prolonged execution times or complete stalls in the process. For example:

Table Size: Indexing a 10 billion row table can be a time-consuming task.

Configuration Settings: Improper settings for maintenance work memory and parallel workers can lead to inefficiencies.

External Constraints: Foreign key constraints and triggers might affect the indexing process, even if they are temporarily disabled.

Locks: Although your test database might not have active transactions, checking for locks is still prudent.

Solution Breakdown

Here are the steps to resolve the hanging issue when executing a CREATE INDEX command.

1. Be Patient

Creating an index is a multi-stage process that can take time. Here’s a brief overview of the stages involved:

Reading the Table: The initial stage reads all records from the table.

Sorting Values: The values must be sorted before the index can be built.

Creating the Index on Disk: Finally, the index files are written to disk.

You may see temporary files growing during this process, which indicates that work is being done. Often, it simply requires more time to finish.

2. Check Temporary Files

During index creation, temporary files can accumulate in the pgsql_tmp directory. If you notice the size of these files growing but the index isn't completing, it might be a sign that the index is still being processed—possibly in the writing phase.

3. Review Your Configuration Settings

Adjusting your PostgreSQL settings can significantly impact performance:

Increase max_parallel_maintenance_workers: You initially set it to 8, but try adjusting it back to a lower number if you're encountering issues. Setting it too high can sometimes overwhelm the system.

Adjust maintenance_work_mem: You've already set it to 2047MB, which is an appropriate amount for Windows, but ensure it's not maxed out based on your system capabilities.

4. Check for Locks

Running the command SELECT * FROM pg_locks; will help you determine if your CREATE INDEX command is blocked by any other processes. It’s important especially if you're using CREATE INDEX CONCURRENTLY, as it involves more complex processing.

Conclusion

If your CREATE INDEX command in PostgreSQL hangs, it can often be attributed to either the size of the data being handled or misconfigured system settings. Whether you need to give it a little extra time, adjust your resource allocation, or check for locks, there are several avenues to explore. Keeping an eye on temporary files can also indicate progress in the indexing process.

By understanding the intricate process behind index creation and patiently allowing it to complete, you can navigate this common challenge effectively. Don’t let a paused command derail your database management efforts—use these insights to empower your PostgreSQL usage.