Watch wait events in pg_stat_activity
wait_event_type and wait_event in pg_stat_activity tell you why a session is not running, waiting on a lock, on the client, or sleeping. Three sessions here show three different causes at a glance.
Problem
What you're actually looking at
The symptom as it shows up on a real server.
A session that is not making progress could be blocked on a lock, waiting for the client to send more data, or deliberately sleeping. pg_stat_activity's wait_event columns name the exact reason, turning 'it's stuck' into a specific diagnosis.
Meridian sees three sessions in odd states. The wait columns immediately distinguish a real lock wait from a session that is merely idle-in-transaction waiting on the client, and from one that is just sleeping.
Simple terms
When a session is not making progress, "it's stuck" is not a diagnosis, you need to know what it is stuck on. pg_stat_activity has two columns, wait_event_type and wait_event, that name the exact reason a backend is parked: waiting on a lock, waiting for the client to send its next command, or just sleeping. One glance turns three mysterious sessions into three specific causes.
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