fix: use a safe checkpoint when cleaning up metadata

crates/core/src/logstore/mod.rs

@@ -161,6 +161,9 @@ pub type LogStoreRef = Arc<dyn LogStore>;
 
 static DELTA_LOG_PATH: LazyLock<Path> = LazyLock::new(|| Path::from("_delta_log"));
 
+pub(crate) static DELTA_LOG_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"(\d{20})\.(json|checkpoint(\.\d+)?\.parquet)$").unwrap());
+
 /// Return the [LogStoreRef] for the provided [Url] location
 ///
 /// This will use the built-in process global [crate::storage::ObjectStoreRegistry] by default
@@ -637,9 +640,6 @@ impl<'de> Deserialize<'de> for LogStoreConfig {
     }
 }
 
-static DELTA_LOG_REGEX: LazyLock<Regex> =
-    LazyLock::new(|| Regex::new(r"(\d{20})\.(json|checkpoint(\.\d+)?\.parquet)$").unwrap());
-
 /// Extract version from a file name in the delta log
 pub fn extract_version_from_filename(name: &str) -> Option<i64> {
     DELTA_LOG_REGEX

crates/core/src/protocol/checkpoints.rs

@@ -6,7 +6,7 @@ use url::Url;
 
 use arrow::compute::filter_record_batch;
 use arrow_array::{BooleanArray, RecordBatch};
-use chrono::Utc;
+use chrono::{TimeZone, Utc};
 use delta_kernel::engine::arrow_data::ArrowEngineData;
 use delta_kernel::engine_data::FilteredEngineData;
 use delta_kernel::last_checkpoint_hint::LastCheckpointHint;
@@ -22,11 +22,14 @@ use tokio::task::spawn_blocking;
 use tracing::{debug, error, warn};
 use uuid::Uuid;
 
-use crate::logstore::{LogStore, LogStoreExt};
+use crate::logstore::{LogStore, LogStoreExt, DELTA_LOG_REGEX};
 use crate::table::config::TablePropertiesExt as _;
 use crate::{open_table_with_version, DeltaTable};
 use crate::{DeltaResult, DeltaTableError};
 
+static CHECKPOINT_REGEX: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"_delta_log/(\d{20})\.(checkpoint).*$").unwrap());
+
 /// Creates checkpoint for a given table version, table state and object store
 pub(crate) async fn create_checkpoint_for(
     version: u64,
@@ -181,92 +184,126 @@ pub async fn create_checkpoint_from_table_uri_and_cleanup(
     Ok(())
 }
 
-/// Deletes all delta log commits that are older than the cutoff time
-/// and less than the specified version.
+/// Delete expired Delta log files up to a safe checkpoint boundary.
+///
+/// This routine removes JSON commit files, in-progress JSON temp files, and
+/// checkpoint files under `_delta_log/` that are both:
+/// - older than the provided `cutoff_timestamp` (milliseconds since epoch), and
+/// - strictly less than the provided `until_version`.
+///
+/// Safety guarantee:
+/// To avoid deleting files that might still be required to reconstruct the
+/// table state at or before the requested cutoff, the function first identifies
+/// the most recent checkpoint whose version is `<= until_version` and whose file
+/// modification time is `<= cutoff_timestamp`. Only files strictly older than
+/// this checkpoint (both by version and timestamp) are considered for deletion.
+/// If no such checkpoint exists (including when there is no `_last_checkpoint`),
+/// the function performs no deletions and returns `Ok(0)`.
+///
+/// See also: https://github.com/delta-io/delta-rs/issues/3692 for background on
+/// why cleanup must align to an existing checkpoint.
 pub async fn cleanup_expired_logs_for(
-    until_version: i64,
+    mut keep_version: i64,
     log_store: &dyn LogStore,
     cutoff_timestamp: i64,
     operation_id: Option<Uuid>,
 ) -> DeltaResult<usize> {
-    static DELTA_LOG_REGEX: LazyLock<Regex> = LazyLock::new(|| {
-        Regex::new(r"_delta_log/(\d{20})\.(json|checkpoint|json.tmp).*$").unwrap()
-    });
-
-    let object_store = log_store.object_store(None);
+    debug!("called cleanup_expired_logs_for");
+    let object_store = log_store.object_store(operation_id);
     let log_path = log_store.log_path();
-    let maybe_last_checkpoint = read_last_checkpoint(&object_store, log_path).await?;
 
-    let Some(last_checkpoint) = maybe_last_checkpoint else {
+    // List all log entries under _delta_log
+    let log_entries: Vec<Result<crate::ObjectMeta, _>> =
+        object_store.list(Some(log_path)).collect().await;
+
+    debug!("starting keep_version: {:?}", keep_version);
+    debug!(
+        "starting cutoff_timestamp: {:?}",
+        Utc.timestamp_millis_opt(cutoff_timestamp).unwrap()
+    );
+
+    // Step 1: Find min_retention_version among DELTA_LOG files with ts >= cutoff_timestamp
+    let min_retention_version = log_entries
+        .iter()
+        .filter_map(|m| m.as_ref().ok())
+        .filter_map(|m| {
+            let path = m.location.as_ref();
+            DELTA_LOG_REGEX
+                .captures(path)
+                .and_then(|caps| caps.get(1))
+                .and_then(|v| v.as_str().parse::<i64>().ok())
+                .map(|ver| (ver, m.last_modified.timestamp_millis()))
+        })
+        .filter(|(_, ts)| *ts >= cutoff_timestamp)
+        .map(|(ver, _)| ver)
+        .min();
+
+    let min_retention_version = min_retention_version.unwrap_or(keep_version);
+
+    // Step 2: Move keep_version down to the minimum version inside the retention period to make sure
+    // every version inside the retention period is kept.
+    keep_version = keep_version.min(min_retention_version);
+
+    // Step 3: Find safe checkpoint with checkpoint_version <= keep_version (no ts restriction)
+    let safe_checkpoint_version_opt = log_entries
+        .iter()
+        .filter_map(|m| m.as_ref().ok())
+        .filter_map(|m| {
+            let path = m.location.as_ref();
+            CHECKPOINT_REGEX
+                .captures(path)
+                .and_then(|caps| caps.get(1))
+                .and_then(|v| v.as_str().parse::<i64>().ok())
+        })
+        .filter(|ver| *ver <= keep_version)
+        .max();
+
+    // Exit if no safe_checkpoint file was found.
+    let Some(safe_checkpoint_version) = safe_checkpoint_version_opt else {
+        debug!(
+            "Not cleaning metadata files, could not find a checkpoint with version <= keep_version ({})",
+            keep_version
+        );
         return Ok(0);
     };
 
-    let until_version = i64::min(until_version, last_checkpoint.version as i64);
+    debug!("safe_checkpoint_version: {}", safe_checkpoint_version);
+
+    // Step 4: Delete DELTA_LOG files where log_ver < safe_checkpoint_version && ts <= cutoff_timestamp
+    let locations = futures::stream::iter(log_entries.into_iter())
+        .filter_map(|meta: Result<crate::ObjectMeta, _>| async move {
+            let meta = match meta {
+                Ok(m) => m,
+                Err(err) => {
+                    error!("Error received while cleaning up expired logs: {err:?}");
+                    return None;
+                }
+            };
+            let path_str = meta.location.as_ref();
+            let captures = DELTA_LOG_REGEX.captures(path_str)?;
+            let ts = meta.last_modified.timestamp_millis();
+            let log_ver_str = captures.get(1).unwrap().as_str();
+            let Ok(log_ver) = log_ver_str.parse::<i64>() else {
+                return None;
+            };
+            if log_ver < safe_checkpoint_version && ts <= cutoff_timestamp {
+                debug!("file to delete: {:?}", meta.location);
+                Some(Ok(meta.location))
+            } else {
+                None
+            }
+        })
+        .boxed();
 
-    // Feed a stream of candidate deletion files directly into the delete_stream
-    // function to try to improve the speed of cleanup and reduce the need for
-    // intermediate memory.
-    let object_store = log_store.object_store(operation_id);
     let deleted = object_store
-        .delete_stream(
-            object_store
-                .list(Some(log_store.log_path()))
-                // This predicate function will filter out any locations that don't
-                // match the given timestamp range
-                .filter_map(|meta: Result<crate::ObjectMeta, _>| async move {
-                    if meta.is_err() {
-                        error!("Error received while cleaning up expired logs: {meta:?}");
-                        return None;
-                    }
-                    let meta = meta.unwrap();
-                    let ts = meta.last_modified.timestamp_millis();
-
-                    match DELTA_LOG_REGEX.captures(meta.location.as_ref()) {
-                        Some(captures) => {
-                            let log_ver_str = captures.get(1).unwrap().as_str();
-                            let log_ver: i64 = log_ver_str.parse().unwrap();
-                            if log_ver < until_version && ts <= cutoff_timestamp {
-                                // This location is ready to be deleted
-                                Some(Ok(meta.location))
-                            } else {
-                                None
-                            }
-                        }
-                        None => None,
-                    }
-                })
-                .boxed(),
-        )
+        .delete_stream(locations)
         .try_collect::<Vec<_>>()
         .await?;
 
     debug!("Deleted {} expired logs", deleted.len());
     Ok(deleted.len())
 }
 
-/// Try reading the `_last_checkpoint` file.
-///
-/// Note that we typically want to ignore a missing/invalid `_last_checkpoint` file without failing
-/// the read. Thus, the semantics of this function are to return `None` if the file is not found or
-/// is invalid JSON. Unexpected/unrecoverable errors are returned as `Err` case and are assumed to
-/// cause failure.
-async fn read_last_checkpoint(
-    storage: &dyn ObjectStore,
-    log_path: &Path,
-) -> DeltaResult<Option<LastCheckpointHint>> {
-    const LAST_CHECKPOINT_FILE_NAME: &str = "_last_checkpoint";
-    let file_path = log_path.child(LAST_CHECKPOINT_FILE_NAME);
-    let maybe_data = storage.get(&file_path).await;
-    let data = match maybe_data {
-        Ok(data) => data.bytes().await?,
-        Err(Error::NotFound { .. }) => return Ok(None),
-        Err(err) => return Err(err.into()),
-    };
-    Ok(serde_json::from_slice(&data)
-        .inspect_err(|e| warn!("invalid _last_checkpoint JSON: {e}"))
-        .ok())
-}
-
 #[cfg(test)]
 mod tests {
     use std::sync::Arc;
@@ -285,6 +322,29 @@ mod tests {
     use crate::writer::test_utils::get_delta_schema;
     use crate::DeltaResult;
 
+    /// Try reading the `_last_checkpoint` file.
+    ///
+    /// Note that we typically want to ignore a missing/invalid `_last_checkpoint` file without failing
+    /// the read. Thus, the semantics of this function are to return `None` if the file is not found or
+    /// is invalid JSON. Unexpected/unrecoverable errors are returned as `Err` case and are assumed to
+    /// cause failure.
+    async fn read_last_checkpoint(
+        storage: &dyn ObjectStore,
+        log_path: &Path,
+    ) -> DeltaResult<Option<LastCheckpointHint>> {
+        const LAST_CHECKPOINT_FILE_NAME: &str = "_last_checkpoint";
+        let file_path = log_path.child(LAST_CHECKPOINT_FILE_NAME);
+        let maybe_data = storage.get(&file_path).await;
+        let data = match maybe_data {
+            Ok(data) => data.bytes().await?,
+            Err(Error::NotFound { .. }) => return Ok(None),
+            Err(err) => return Err(err.into()),
+        };
+        Ok(serde_json::from_slice(&data)
+            .inspect_err(|e| warn!("invalid _last_checkpoint JSON: {e}"))
+            .ok())
+    }
+
     #[tokio::test]
     async fn test_create_checkpoint_for() {
         let table_schema = get_delta_schema();

crates/core/tests/checkpoint_writer.rs

@@ -196,7 +196,7 @@ mod delete_expired_delta_log_in_checkpoint {
             Some(HashMap::from([
                 (
                     TableProperty::LogRetentionDuration.as_ref().into(),
-                    Some("interval 10 minute".to_string()),
+                    Some("interval 0 minute".to_string()),
                 ),
                 (
                     TableProperty::EnableExpiredLogCleanup.as_ref().into(),
@@ -225,8 +225,8 @@ mod delete_expired_delta_log_in_checkpoint {
 
         // set last_modified
         set_file_last_modified(0, 25 * 60 * 1000); // 25 mins ago, should be deleted
-        set_file_last_modified(1, 15 * 60 * 1000); // 25 mins ago, should be deleted
-        set_file_last_modified(2, 5 * 60 * 1000); // 25 mins ago, should be kept
+        set_file_last_modified(1, 15 * 60 * 1000); // 15 mins ago, should be deleted
+        set_file_last_modified(2, 5 * 60 * 1000); // 5 mins ago, should be kept as last safe checkpoint
 
         table.load_version(0).await.expect("Cannot load version 0");
         table.load_version(1).await.expect("Cannot load version 1");
@@ -267,6 +267,104 @@ mod delete_expired_delta_log_in_checkpoint {
         table.load_version(2).await.expect("Cannot load version 2");
     }
 
+    // Test to verify that intermediate versions can still be loaded after the checkpoint is created.
+    // This is to verify the behavior of `cleanup_expired_logs_for` and its use of safe checkpoints.
+    #[tokio::test]
+    async fn test_delete_expired_logs_safe_checkpoint() {
+        // For additional tracing:
+        // let _ = pretty_env_logger::try_init();
+        let mut table = fs_common::create_table(
+            "../test/tests/data/checkpoints_with_expired_logs/expired_with_checkpoint",
+            Some(HashMap::from([
+                (
+                    TableProperty::LogRetentionDuration.as_ref().into(),
+                    Some("interval 10 minute".to_string()),
+                ),
+                (
+                    TableProperty::EnableExpiredLogCleanup.as_ref().into(),
+                    Some("true".to_string()),
+                ),
+            ])),
+        )
+        .await;
+
+        let table_path = table.table_uri();
+        let set_file_last_modified = |version: usize, last_modified_millis: u64, suffix: &str| {
+            let path = format!("{table_path}_delta_log/{version:020}.{suffix}");
+            let file = OpenOptions::new().write(true).open(path).unwrap();
+            let last_modified = SystemTime::now().sub(Duration::from_millis(last_modified_millis));
+            let times = FileTimes::new()
+                .set_modified(last_modified)
+                .set_accessed(last_modified);
+            file.set_times(times).unwrap();
+        };
+
+        // create 4 commits
+        let a1 = fs_common::add(0);
+        let a2 = fs_common::add(0);
+        let a3 = fs_common::add(0);
+        let a4 = fs_common::add(0);
+        assert_eq!(1, fs_common::commit_add(&mut table, &a1).await);
+        assert_eq!(2, fs_common::commit_add(&mut table, &a2).await);
+        assert_eq!(3, fs_common::commit_add(&mut table, &a3).await);
+        assert_eq!(4, fs_common::commit_add(&mut table, &a4).await);
+
+        // set last_modified
+        set_file_last_modified(0, 25 * 60 * 1000, "json"); // 25 mins ago, should be deleted
+        set_file_last_modified(1, 20 * 60 * 1000, "json"); // 20 mins ago, last safe checkpoint, should be kept
+        set_file_last_modified(2, 15 * 60 * 1000, "json"); // 15 mins ago, fails retention cutoff, but needed by v3
+        set_file_last_modified(3, 6 * 60 * 1000, "json"); // 6 mins ago, should be kept by retention cutoff
+        set_file_last_modified(4, 5 * 60 * 1000, "json"); // 5 mins ago, should be kept by retention cutoff
+
+        table.load_version(0).await.expect("Cannot load version 0");
+        table.load_version(1).await.expect("Cannot load version 1");
+        table.load_version(2).await.expect("Cannot load version 2");
+        table.load_version(3).await.expect("Cannot load version 3");
+        table.load_version(4).await.expect("Cannot load version 4");
+
+        // Create checkpoint for version 1
+        checkpoints::create_checkpoint_from_table_uri_and_cleanup(
+            deltalake_core::ensure_table_uri(&table.table_uri()).unwrap(),
+            1,
+            Some(false),
+            None,
+        )
+        .await
+        .unwrap();
+
+        // Update checkpoint time for version 1 to be just after version 1 data
+        set_file_last_modified(1, 20 * 60 * 1000 - 10, "checkpoint.parquet");
+
+        // Checkpoint final version
+        checkpoints::create_checkpoint_from_table_uri_and_cleanup(
+            deltalake_core::ensure_table_uri(&table.table_uri()).unwrap(),
+            table.version().unwrap(),
+            None,
+            None,
+        )
+        .await
+        .unwrap();
+
+        table.update().await.unwrap(); // make table to read the checkpoint
+        assert_eq!(
+            table
+                .snapshot()
+                .unwrap()
+                .file_paths_iter()
+                .collect::<Vec<_>>(),
+            vec![
+                ObjectStorePath::from(a4.path.as_ref()),
+                ObjectStorePath::from(a3.path.as_ref()),
+                ObjectStorePath::from(a2.path.as_ref()),
+                ObjectStorePath::from(a1.path.as_ref()),
+            ]
+        );
+
+        // Without going back to a safe checkpoint, previously loading version 3 would fail.
+        table.load_version(3).await.expect("Cannot load version 3");
+        table.load_version(4).await.expect("Cannot load version 4");
+    }
+
     #[tokio::test]
     async fn test_not_delete_expired_logs() {
         let mut table = fs_common::create_table(