When and Why PostgreSQL Indexes Are Ignored

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2024-04-23 18:30:06

While it's true the most problems can be solved by the appropriate use of the index, there are cases where you will just waste resources doing so. For casual developer it might seems like PostgreSQL decided to do its own thing, but when you look behind the scenes it all makes perfect sense. Here's a quick run down of the some reasons why planner might pass on index and rather do things without it.

In the evolution of the software developer journey into the realms of databases, the partial indexes are the next best thing. Why to create the full index where you can easily restrict it to the sub-set of the records? The trick is ensure every query aligns with the condition given during the index creation.

Think of an order management system, where most active orders are going to those in 'open' status. Most of the day-to-day operational tasks will resolve around those entries, a partial index like

provides a perfect match. It will allow to iterate only on a relatively small subset of the data, hence saving the disc space. As long as the application developers are aware of the partial condition, and how to use it. Some