PostgreSQL 10 High Performance - Third Edition

Querying enable parameters

It's possible to disable many of the query planner's techniques, in hopes of avoiding a known bad type of query. This is sometimes used as a work-around for the fact that PostgreSQL doesn't support direct optimizer hints for how to execute a query.

You might see the following code snippet, suggested as a way to force use of indexes instead of sequential scans, for example:

enable_seqscan = off 

Generally, this is a bad idea, and you should improve the information the query optimizer is working with so it makes the right decisions instead. This topic is covered in Chapter 10, Query Optimization.