fn update_snapshot_log()

in crates/iceberg/src/spec/table_metadata_builder.rs [979:1019]

• 32 lines of code
• 9 McCabe index (conditional complexity)

    fn update_snapshot_log(&mut self) -> Result<()> {
        let intermediate_snapshots = self.get_intermediate_snapshots();
        let has_removed_snapshots = self
            .changes
            .iter()
            .any(|update| matches!(update, TableUpdate::RemoveSnapshots { .. }));

        if intermediate_snapshots.is_empty() && !has_removed_snapshots {
            return Ok(());
        }

        let mut new_snapshot_log = Vec::new();
        for log_entry in &self.metadata.snapshot_log {
            let snapshot_id = log_entry.snapshot_id;
            if self.metadata.snapshots.contains_key(&snapshot_id) {
                if !intermediate_snapshots.contains(&snapshot_id) {
                    new_snapshot_log.push(log_entry.clone());
                }
            } else if has_removed_snapshots {
                // any invalid entry causes the history before it to be removed. otherwise, there could be
                // history gaps that cause time-travel queries to produce incorrect results. for example,
                // if history is [(t1, s1), (t2, s2), (t3, s3)] and s2 is removed, the history cannot be
                // [(t1, s1), (t3, s3)] because it appears that s3 was current during the time between t2
                // and t3 when in fact s2 was the current snapshot.
                new_snapshot_log.clear();
            }
        }

        if let Some(current_snapshot_id) = self.metadata.current_snapshot_id {
            let last_id = new_snapshot_log.last().map(|entry| entry.snapshot_id);
            if last_id != Some(current_snapshot_id) {
                return Err(Error::new(
                    ErrorKind::DataInvalid,
                    "Cannot set invalid snapshot log: latest entry is not the current snapshot",
                ));
            }
        };

        self.metadata.snapshot_log = new_snapshot_log;
        Ok(())
    }