stat_activity_autovacuum: collected metric was collected before with the same name and label values

What did you do?

Investigated scrape failures.

What did you expect to see?

No scrape failures.

What did you see instead? Under which circumstances?

$ curl http://localhost:9187/metrics
collected metric "pg_stat_activity_autovacuum_timestamp_seconds" { label:{name:"relname"  value:"datacdr"}  gauge:{value:1.699456188197915e+09}} was collected before with the same name and label values

Given this output it seems likely the stat_activity_autovacuum collector neglects to put the schema name into labels.

• System information:

$ uname -srm
Linux 4.19.0-25-amd64 x86_64

$ lsb_release -a
Distributor ID: Debian
Description:    Debian GNU/Linux 10 (buster)
Release:        10
Codename:       buster

• postgres_exporter version:

$ /usr/local/bin/postgres_exporter --version
postgres_exporter, version 0.15.0 (branch: HEAD, revision: 68c176b8833b7580bf847cecf60f8e0ad5923f9a)
  build user:       root@88f74f2c2888
  build date:       20231027-14:38:56
  go version:       go1.21.3
  platform:         linux/amd64
  tags:             unknown

• postgres_exporter flags:

--collector.stat_statements --collector.stat_wal_receiver --collector.stat_activity_autovacuum --collector.long_running_transactions --collector.database_wraparound

• PostgreSQL version:

# show server_version;
         server_version
--------------------------------
 15.4 (Debian 15.4-2.pgdg100+1)

• Logs:

I didn't see any relevant logs for this.

Start at the stat_activity_autovacuum collector entry point and reproduce the duplicate metric through the /metrics endpoint with the reported PostgreSQL setup. Check how relname and schema are represented in the collected labels; done means the collector emits unique metric label sets without scrape failures.