add postgres slow query note

content/notes/debugging slow postgres queries.md

@@ -0,0 +1,35 @@
+---
+title: Debugging slow PostgreSQL queries
+date: 2024-05-14
+tags:
+  - postgresql
+---
+
+Earlier today I was trying to figure out why I was getting the occasional latency spike. I suspected I had some slow queries that needed optimising, but in order to check I needed to enable slow query logging.
+
+If you wish to log all statements that take longer than 100ms with postgres, add this to your config file
+
+```
+log_min_duration_statement = 100
+```
+
+Then reload the postgres config with 
+
+```
+select pg_reload_conf();
+```
+
+No restart of the server required!
+
+Otherwise, the following options can be helpful
+
+```ini
+# Log all statements, not just the slow ones
+# This may be very chatty, so make sure your log partition doesn't fill up
+log_statement = all/ddl/none
+```
+
+```ini
+# Log durations alongside statements
+log_duration = on
+```