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Tips for a Healthier Postgres Database

It’s been a busy year building
Crunchy Bridge and we’ve shipped a lot of
new awesome things. Instead of doing a wrap-up of all the growth and exciting
features, instead I wanted to take the time to try to teach a few more things to
those that follow us. While onboarding customer after customer this year I’ve
noted a few key things everyone should put in place right away – to either
improve the health of your database or to save yourself from a bad day.

Set a statement timeout

Long running (usually unintentionally so) queries can wreck havoc on a database.
They can hold up other queries, replication, or other database processes. Most
applications are designed for typical queries to run in a few milliseconds. You
may have long running queries for reporting, but these are best offloaded to a
read replica for reporting and analytics. To prevent those long running queries
you can set a statement_timeout:

ALTER DATABASE mydatabase SET statement_timeout = '60s';

For good measure you may also want to set your idle_in_transaction timeout as
well, which will cancel long running transaction that are no longer performing

Ensure you have query tracking

Understanding what is going on inside your database is always a good idea. Which
queries are slow? Which queries are run too many times? Enter the most useful
Postgres extension that exists: pg_stat_statements.

Pg_stat_statements records every query that runs against your database,
parameterizes it, and then records a variety of metrics about it. That makes it
easy to answer the above questions. If you don’t have it installed already do it
today by running:

CREATE EXTENSION pg_stat_statements;

Once it’s in place you can take a look at our
deep dive
on all the insights it can show you.

Log slow running queries

While pg_stat_statements is useful for looking at frequently run queries or
queries that may always be slow, sometimes you have extreme outlier queries.
With pg_stat_statements you may review your queries every few months.
Meanwhile your Postgres logs likely
feed into some other central
system that you are monitoring daily and have alerting on. Catching these slow
outlier queries early can be a great canary for things you should quickly move
off to a read-replica for scaling or that you should rewrite to be more
efficient. You can
log all slow queries
that take over a certain time with log_min_duration_statement.

For many SaaS applications setting your log_min_duration_statement to
something like 1 second: 1s or even as low as 100 milliseconds: 100ms can be
a big asset.

Improve your connection management

If you’re using Rails, Django, Hibernate or any other framework/ORM you’ve
likely set a connection pool in your application settings for your database.
That connection pool is likely reducing latency in new connections to your
database, but is also limiting the performance available for your database. On
versions prior to Postgres 14, connections consumed extra overhead leaving
idle connections as wasted space. The solution to this is not to replace your
in app connection pooling, but rather add a server side connection pooler such
as PgBouncer. With PgBouncer you’re able to scale to 10s of thousands of
connections with no problem. You can take a quick look at your existing database
to see if PgBouncer would help:

SELECT count(*),
FROM pg_stat_activity

If you see idle is above 20 it’s recommended to explore using PgBouncer.
Adding PgBouncer is often a no brainer to get better performance without any
heavy refactoring required. And to make it easy if you’re on
Crunchy Bridge it’s already
available to you.

Find your goldilocks range for indexes

There seems to be a common lifecycle of indexes within applications. First you
start off with almost none, maybe a few on primary keys. Then you start adding
them, one by one, two by two, until you’ve got quite a few indexes for most any
query you can run. Something is slow? Throw an index at it. What you end up with
is some contention on overall throughput of your database, and well a lot of
indexes that became a tangled ball of yarn over time.

We’ve got a slew of write-ups and guides on indexes and unfortunately there
isn’t a “this is your one thing to read and your done”. But a few key things and
you can be in a better place:

Here’s to less database problems in 2022

Our goal at Crunchy is to make Postgres great. One part of that is helping our
customers understand their database and providing them with support and guidance
for all their Postgres needs.

With Crunchy Bridge
we’re working towards making all of the above easier, so it’s one less thing you
have to worry about. We’ve already had customers migrate and see
3-5x performance improvement
over their existing cloud providers. We know if you’re here you’re already a fan
of Postgres. In this coming year we look forward to making the developer
experience of Postgres better than it’s ever been.

Craig Kerstiens

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