Function trim_change_log 

pub async fn trim_change_log(
    pool: &PgPool,
    before: DateTime<Utc>,
) -> Result<u64>

Delete every change-log row with created_at < before. Returns the number of rows deleted.

Run periodically from a background task; the reactor’s gap-recovery only needs the recent tail. Default retention in the framework is 1 hour, set by passing Utc::now() - chrono::Duration::hours(1).

Trimming is skipped when the total row count is at or below [CHANGE_LOG_MIN_ROWS] (default 1 000). This prevents over-aggressive cleanup on quiet systems where entries age past the window but the log itself is small.

Uses pg_try_advisory_xact_lock with the LeaderRole::LogCompactor lock ID so that only one node in the cluster runs the DELETE at a time. If another node already holds the lock the function returns Ok(0) immediately rather than blocking or racing.