PGLABEL is documented but not honored by postgres plugins in debian distribution

[pjungwir]

Describe the bug

The perldoc in Pgsql.pm says you can set env.PGLABEL to add some extra text to the graph title, but it doesn't do anything. This is very useful when you are running multiple postgres clusters (as the perldoc says).

This was added in 2013 and works on master, but the debian branch includes only the perldoc, not the implementation. It looks like the perldoc was included in an unrelated commit by mistake, and somehow the implementation was never merged.

It would be very convenient to have this feature!

To Reproduce

On a bookworm system:

apt-get install munin-node
ln -s /usr/share/munin/plugins/postgres_checkpoints /etc/munin/plugins/postgres_16_checkpoints
cat > /etc/munin/plugin-conf.d/postgres <<'EOF'
[postgres_16_checkpoints]
env.PGLABEL v16
EOF
munin-run postgres_16_checkpoints config | grep graph_title

Expected behavior

I want to see:

graph_title PostgreSQL checkpoints v16

Instead I get:

graph_title PostgreSQL checkpoints