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stat_replication: fix "slot_name does not exist" by joining pg_replication_slots #1313

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stat_replication: fix "slot_name does not exist" by joining pg_replication_slots #1313

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2 changes: 1 addition & 1 deletion CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
* [CHANGE] ...
* [FEATURE] ...
* [ENHANCEMENT] ...
* [BUGFIX] ...
* [BUGFIX] stat_replication: fix "slot_name does not exist" by joining `pg_replication_slots` (closes #1310)

## 0.19.1 / 2026-02-25

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10 changes: 8 additions & 2 deletions collector/pg_stat_replication.go
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Expand Up @@ -55,25 +55,31 @@ var (
prometheus.Labels{},
)

// slot_name is not a column of pg_stat_replication; it lives on
// pg_replication_slots and is linked via the standby's WAL sender
// PID. LEFT JOIN so clients that do not use a named slot still get
// a row with an empty slot_name label.
statReplicationQuery = `
SELECT
application_name,
client_addr::text,
state,
slot_name,
s.slot_name,
(case pg_is_in_recovery() when 't' then pg_wal_lsn_diff(pg_last_wal_receive_lsn(), pg_lsn('0/0'))::float else pg_wal_lsn_diff(pg_current_wal_lsn(), pg_lsn('0/0'))::float end) AS pg_current_wal_lsn_bytes,
(case pg_is_in_recovery() when 't' then pg_wal_lsn_diff(pg_last_wal_receive_lsn(), replay_lsn)::float else pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn)::float end) AS pg_wal_lsn_diff
FROM pg_stat_replication
LEFT JOIN pg_replication_slots s ON s.active_pid = pg_stat_replication.pid
`

statReplicationQueryBefore10 = `
SELECT
application_name,
client_addr::text,
state,
slot_name,
s.slot_name,
(case pg_is_in_recovery() when 't' then pg_xlog_location_diff(pg_last_xlog_receive_location(), replay_location)::float else pg_xlog_location_diff(pg_current_xlog_location(), replay_location)::float end) AS pg_xlog_location_diff
FROM pg_stat_replication
LEFT JOIN pg_replication_slots s ON s.active_pid = pg_stat_replication.pid

@ArthurSens ArthurSens Jul 4, 2026

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Seems like this query only works for postgres 9.5 and above, because active_pid was only added in PG 9.5.x. See https://www.postgresql.org/docs/9.5/view-pg-replication-slots.html and https://www.postgresql.org/docs/9.4/catalog-pg-replication-slots.html

Could you please have a query for 9.4 and below that doesn't include slot_name?

`
)

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