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fix: use pg_lsn cast for LSN comparison in slot advance resource #391

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Merged
tsivaprasad merged 1 commit into from
May 25, 2026
Merged

fix: use pg_lsn cast for LSN comparison in slot advance resource #391

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8 changes: 5 additions & 3 deletions server/internal/database/replication_slot_advance_from_cts_resource.go
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Original file line number Diff line number Diff line change
Expand Up @@ -133,9 +133,11 @@ func (r *ReplicationSlotAdvanceFromCTSResource) Create(ctx context.Context, rc *
return fmt.Errorf("failed to query target replication slot lsn: %w", err)
}

if targetLSN <= currentLSN {
// No need to advance if the slot is already ahead of the commit
// timestamp
atOrBefore, err := postgres.LsnAtOrBefore(targetLSN, currentLSN).Scalar(ctx, conn)
if err != nil {
return fmt.Errorf("failed to compare LSNs: %w", err)
}
if atOrBefore {
return nil
}

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10 changes: 10 additions & 0 deletions server/internal/postgres/create_db.go
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Expand Up @@ -448,6 +448,16 @@ func SpockProgressReachedLSN(peerNodeName, targetLSN string) Query[bool] {
}
}

// LsnAtOrBefore reports whether lsn1 <= lsn2 using PostgreSQL's pg_lsn type.
// Use this instead of Go string comparison — LSNs are hex-formatted and string
// ordering produces wrong results across segment boundaries (e.g. "F/..." > "10/...").
func LsnAtOrBefore(lsn1, lsn2 string) Query[bool] {
return Query[bool]{
SQL: "SELECT @lsn1::pg_lsn <= @lsn2::pg_lsn",
Args: pgx.NamedArgs{"lsn1": lsn1, "lsn2": lsn2},
}
}

// GetSubscriptionStatus returns the current status of a specific subscription
func GetSubscriptionStatus(providerNode, subscriberNode string) Query[string] {
return Query[string]{
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