Function preview_unrecord

atomic-repository/src/unrecord.rs:615–658

Preview what would be unrecorded without actually doing it. # Arguments `txn` - Read transaction `view` - View to preview `hashes` - Hashes of changes to unrecord `options` - Unrecord options # Returns An `UnrecordOutcome` describing what would happen.

(
    txn: &T,
    view: &ViewState,
    hashes: &[Hash],
    options: &UnrecordOptions,
)

///
/// An `UnrecordOutcome` describing what would happen.
pub fn preview_unrecord<T: ViewTxnT>(
    txn: &T,
    view: &ViewState,
    hashes: &[Hash],
    options: &UnrecordOptions,
) -> UnrecordResult<UnrecordOutcome> {
    let mut all_unrecords = Vec::new();

    for hash in hashes {
        if options.cascade {
            let set = find_unrecord_set(txn, view, hash, options.max_cascade)?;
            for h in set {
                if !all_unrecords.contains(&h) {
                    all_unrecords.push(h);
                }
            }
        } else {
            // Check if can unrecord without cascade
            let info = check_can_unrecord(txn, view, hash, options)?;
            if !info.can_unrecord {
                return Err(UnrecordError::HasDependents {
                    hash: hash.to_base32(),
                    dependents: info.dependents.iter().map(|h| h.to_base32()).collect(),
                });
            }
            if !all_unrecords.contains(hash) {
                all_unrecords.push(*hash);
            }
        }
    }

    // Compute new state
    let removed_set: HashSet<Hash> = all_unrecords.iter().copied().collect();
    let new_state = compute_state_after_unrecord(txn, view, &removed_set)?;
    let new_count = view.change_count - all_unrecords.len() as u64;

    let mut stats = UnrecordStats::new();
    stats.direct_unrecords = hashes.len();
    stats.cascaded_unrecords = all_unrecords.len() - hashes.len();

    Ok(UnrecordOutcome::new(all_unrecords, new_state, new_count)
        .as_dry_run()
        .with_stats(stats))
}

/// Get the sequence number of the last change in a view.
///