Showing posts from October, 2019

Using PostgreSQL as a cache?

In the article on his blog Peter asks "How much faster is Redis at storing a blob of JSON compared to PostgreSQL?". Answer: 14x slower.

Seems about right. Usually Redis is about 4x faster for a simple query like that compared to using PostgreSQL as a cache in my experience. It's why so many people use Redis as a cache. But I'd suggest PostgreSQL is good enough to act as a cache for many people.

Django is pretty slow at fetching from PostgreSQL compared to other python options, so this could explain part of the 14x VS 4x difference.

Note that Django should be adding an index because of ForeignKey. However it's possible it isn't being used, or the table may need to analyze stats again. Also note that Django does not support prepared statements built in, and when you don't use prepared statements you do not use the PostgreSQL query cache. Prepared statements can give a 50% speedup often, because they don't have to do the query parsing and do a new quer…