How Can I Force Index Usage in PostgreSQL, and Why Shouldn't I Do It in Production?

Pros and cons of forced use of PostgreSQL indexes

Many database systems support index hints, but PostgreSQL intentionally does not provide this functionality. This is because forcing the use of a specific index may impact performance optimization, and data changes over time may also cause indexes to become invalid.

How to replace index hints

PostgreSQL’s query optimizer will continuously monitor and adjust query plans based on statistical information. However, if you must force a specific index, you can use the following method:

uses the enable_seqscan and enable_indexscan parameters

These two parameters allow you to disable sequential scans or force index scans.

<code class="language-sql">SET enable_seqscan = off;
SET enable_indexscan = on;</code>

Warning: These methods are recommended for testing purposes only and should not be used in a production environment. For ongoing performance issues, check the documentation to troubleshoot query performance issues.

Reason for default behavior

For small tables or when the data type does not match the index, PostgreSQL may deliberately choose to scan sequentially. Additionally, incorrect planner settings can result in suboptimal query plans.

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