[write] add Transaction with commit info and commit implementation

ffi/src/lib.rs

@@ -329,6 +329,9 @@ pub enum KernelError {
     InternalError,
     InvalidExpression,
     InvalidLogPath,
+    InvalidCommitInfo,
+    FileAlreadyExists,
+    MissingCommitInfo,
 }
 
 impl From<Error> for KernelError {
@@ -376,6 +379,9 @@ impl From<Error> for KernelError {
             } => Self::from(*source),
             Error::InvalidExpressionEvaluation(_) => KernelError::InvalidExpression,
             Error::InvalidLogPath(_) => KernelError::InvalidLogPath,
+            Error::InvalidCommitInfo(_) => KernelError::InvalidCommitInfo,
+            Error::FileAlreadyExists(_) => KernelError::FileAlreadyExists,
+            Error::MissingCommitInfo => KernelError::MissingCommitInfo,
         }
     }
 }

kernel/Cargo.toml

@@ -36,6 +36,8 @@ delta_kernel_derive = { path = "../derive-macros", version = "0.4.0" }
 # used for developer-visibility
 visibility = "0.1.1"
 
+# Used in the sync engine
+tempfile = { version = "3", optional = true }
 # Used in default engine
 arrow-buffer = { workspace = true, optional = true }
 arrow-array = { workspace = true, optional = true, features = ["chrono-tz"] }
@@ -99,6 +101,7 @@ sync-engine = [
   "arrow-json",
   "arrow-select",
   "parquet",
+  "tempfile",
 ]
 integration-test = [
   "hdfs-native-object-store/integration-test",

kernel/src/actions/mod.rs

@@ -46,6 +46,10 @@ static LOG_SCHEMA: LazyLock<SchemaRef> = LazyLock::new(|| {
     .into()
 });
 
+static LOG_COMMIT_INFO_SCHEMA: LazyLock<SchemaRef> = LazyLock::new(|| {
+    StructType::new([Option::<CommitInfo>::get_struct_field(COMMIT_INFO_NAME)]).into()
+});
+
 #[cfg_attr(feature = "developer-visibility", visibility::make(pub))]
 #[cfg_attr(not(feature = "developer-visibility"), visibility::make(pub(crate)))]
 fn get_log_schema() -> &'static SchemaRef {
@@ -58,6 +62,10 @@ fn get_log_add_schema() -> &'static SchemaRef {
     &LOG_ADD_SCHEMA
 }
 
+pub(crate) fn get_log_commit_info_schema() -> &'static SchemaRef {
+    &LOG_COMMIT_INFO_SCHEMA
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Schema)]
 pub struct Format {
     /// Name of the encoding for files in this table
@@ -147,8 +155,26 @@ impl Protocol {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Schema)]
-pub struct CommitInfo {
-    pub kernel_version: Option<String>,
+#[cfg_attr(feature = "developer-visibility", visibility::make(pub))]
+#[cfg_attr(not(feature = "developer-visibility"), visibility::make(pub(crate)))]
+struct CommitInfo {
+    /// The time this logical file was created, as milliseconds since the epoch.
+    /// Read: optional, write: required (that is, kernel always writes).
+    /// If in-commit timestamps are enabled, this is always required.
+    pub(crate) timestamp: Option<i64>,
+    /// An arbitrary string that identifies the operation associated with this commit. This is
+    /// specified by the engine. Read: optional, write: required (that is, kernel alwarys writes).
+    pub(crate) operation: Option<String>,
+    /// Map of arbitrary string key-value pairs that provide additional information about the
+    /// operation. This is specified by the engine. For now this is always empty on write.
+    pub(crate) operation_parameters: Option<HashMap<String, String>>,
+    /// The version of the delta_kernel crate used to write this commit. The kernel will always
+    /// write this field, but it is optional since many tables will not have this field (i.e. any
+    /// tables not written by kernel).
+    pub(crate) kernel_version: Option<String>,
+    /// A place for the engine to store additional metadata associated with this commit encoded as
+    /// a map of strings.
+    pub(crate) engine_commit_info: Option<HashMap<String, String>>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Schema)]
@@ -427,4 +453,32 @@ mod tests {
         )]));
         assert_eq!(schema, expected);
     }
+
+    #[test]
+    fn test_commit_info_schema() {
+        let schema = get_log_schema()
+            .project(&["commitInfo"])
+            .expect("Couldn't get commitInfo field");
+
+        let expected = Arc::new(StructType::new(vec![StructField::new(
+            "commitInfo",
+            StructType::new(vec![
+                StructField::new("timestamp", DataType::LONG, true),
+                StructField::new("operation", DataType::STRING, true),
+                StructField::new(
+                    "operationParameters",
+                    MapType::new(DataType::STRING, DataType::STRING, false),
+                    true,
+                ),
+                StructField::new("kernelVersion", DataType::STRING, true),
+                StructField::new(
+                    "engineCommitInfo",
+                    MapType::new(DataType::STRING, DataType::STRING, false),
+                    true,
+                ),
+            ]),
+            true,
+        )]));
+        assert_eq!(schema, expected);
+    }
 }

kernel/src/engine/arrow_utils.rs

@@ -16,7 +16,7 @@ use arrow_array::{
     cast::AsArray, new_null_array, Array as ArrowArray, GenericListArray, OffsetSizeTrait,
     RecordBatch, StringArray, StructArray,
 };
-use arrow_json::ReaderBuilder;
+use arrow_json::{LineDelimitedWriter, ReaderBuilder};
 use arrow_schema::{
     DataType as ArrowDataType, Field as ArrowField, FieldRef as ArrowFieldRef, Fields,
     SchemaRef as ArrowSchemaRef,
@@ -662,6 +662,21 @@ fn parse_json_impl(json_strings: &StringArray, schema: ArrowSchemaRef) -> DeltaR
     Ok(concat_batches(&schema, output.iter())?)
 }
 
+/// serialize an arrow RecordBatch to a JSON string by appending to a buffer.
+// TODO (zach): this should stream data to the JSON writer and output an iterator.
+pub(crate) fn to_json_bytes(
+    data: impl Iterator<Item = Box<dyn EngineData>> + Send,
+) -> DeltaResult<Vec<u8>> {
+    let mut writer = LineDelimitedWriter::new(Vec::new());
+    for chunk in data.into_iter() {
+        let arrow_data = ArrowEngineData::try_from_engine_data(chunk)?;
+        let record_batch = arrow_data.record_batch();
+        writer.write(record_batch)?;
+    }
+    writer.finish()?;
+    Ok(writer.into_inner())
+}
+
 #[cfg(test)]
 mod tests {
     use std::sync::Arc;
@@ -1408,4 +1423,24 @@ mod tests {
         assert_eq!(mask_indices, expect_mask);
         assert_eq!(reorder_indices, expect_reorder);
     }
+
+    #[test]
+    fn test_write_json() -> DeltaResult<()> {
+        let schema = Arc::new(ArrowSchema::new(vec![ArrowField::new(
+            "string",
+            ArrowDataType::Utf8,
+            true,
+        )]));
+        let data = RecordBatch::try_new(
+            schema.clone(),
+            vec![Arc::new(StringArray::from(vec!["string1", "string2"]))],
+        )?;
+        let data: Box<dyn EngineData> = Box::new(ArrowEngineData::new(data));
+        let json = to_json_bytes(Box::new(std::iter::once(data)))?;
+        assert_eq!(
+            json,
+            "{\"string\":\"string1\"}\n{\"string\":\"string2\"}\n".as_bytes()
+        );
+        Ok(())
+    }
 }

kernel/src/engine/default/json.rs

@@ -11,10 +11,12 @@ use bytes::{Buf, Bytes};
 use futures::{StreamExt, TryStreamExt};
 use object_store::path::Path;
 use object_store::{DynObjectStore, GetResultPayload};
+use url::Url;
 
 use super::executor::TaskExecutor;
 use super::file_stream::{FileOpenFuture, FileOpener, FileStream};
 use crate::engine::arrow_utils::parse_json as arrow_parse_json;
+use crate::engine::arrow_utils::to_json_bytes;
 use crate::schema::SchemaRef;
 use crate::{
     DeltaResult, EngineData, Error, ExpressionRef, FileDataReadResultIterator, FileMeta,
@@ -89,6 +91,31 @@ impl<E: TaskExecutor> JsonHandler for DefaultJsonHandler<E> {
             self.readahead,
         )
     }
+
+    // note: for now we just buffer all the data and write it out all at once
+    fn write_json_file(
+        &self,
+        path: &Url,
+        data: Box<dyn Iterator<Item = Box<dyn EngineData>> + Send>,
+        _overwrite: bool,
+    ) -> DeltaResult<()> {
+        let buffer = to_json_bytes(data)?;
+        // Put if absent
+        let store = self.store.clone(); // cheap Arc
+        let path = Path::from(path.path());
+        let path_str = path.to_string();
+        self.task_executor
+            .block_on(async move {
+                store
+                    .put_opts(&path, buffer.into(), object_store::PutMode::Create.into())
+                    .await
+            })
+            .map_err(|e| match e {
+                object_store::Error::AlreadyExists { .. } => Error::FileAlreadyExists(path_str),
+                e => e.into(),
+            })?;
+        Ok(())
+    }
 }
 
 /// A [`FileOpener`] that opens a JSON file and yields a [`FileOpenFuture`]

kernel/src/engine/sync/json.rs

@@ -1,13 +1,17 @@
-use std::{fs::File, io::BufReader};
+use std::{fs::File, io::BufReader, io::Write};
 
 use arrow_schema::SchemaRef as ArrowSchemaRef;
+use tempfile::NamedTempFile;
+use url::Url;
 
 use super::read_files;
 use crate::engine::arrow_data::ArrowEngineData;
 use crate::engine::arrow_utils::parse_json as arrow_parse_json;
+use crate::engine::arrow_utils::to_json_bytes;
 use crate::schema::SchemaRef;
 use crate::{
-    DeltaResult, EngineData, ExpressionRef, FileDataReadResultIterator, FileMeta, JsonHandler,
+    DeltaResult, EngineData, Error, ExpressionRef, FileDataReadResultIterator, FileMeta,
+    JsonHandler,
 };
 
 pub(crate) struct SyncJsonHandler;
@@ -41,4 +45,98 @@ impl JsonHandler for SyncJsonHandler {
     ) -> DeltaResult<Box<dyn EngineData>> {
         arrow_parse_json(json_strings, output_schema)
     }
+
+    // For sync writer we write data to a tmp file then atomically rename it to the final path.
+    // This is highly OS-dependent and for now relies on the atomicity of tempfile's
+    // `persist_noclobber`.
+    fn write_json_file(
+        &self,
+        path: &Url,
+        data: Box<dyn Iterator<Item = Box<dyn EngineData>> + Send>,
+        _overwrite: bool,
+    ) -> DeltaResult<()> {
+        let path = path
+            .to_file_path()
+            .map_err(|_| crate::Error::generic("sync client can only read local files"))?;
+        let Some(parent) = path.parent() else {
+            return Err(crate::Error::generic(format!(
+                "no parent found for {:?}",
+                path
+            )));
+        };
+
+        // write data to tmp file
+        let mut tmp_file = NamedTempFile::new_in(parent)?;
+        let buf = to_json_bytes(data)?;
+        tmp_file.write_all(&buf)?;
+        tmp_file.flush()?;
+
+        // use 'persist_noclobber' to atomically rename tmp file to final path
+        tmp_file
+            .persist_noclobber(path.clone())
+            .map_err(|e| match e {
+                tempfile::PersistError { error, .. }
+                    if error.kind() == std::io::ErrorKind::AlreadyExists =>
+                {
+                    Error::FileAlreadyExists(path.to_string_lossy().to_string())
+                }
+                e => Error::IOError(e.into()),
+            })?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use std::sync::Arc;
+
+    use arrow_array::{RecordBatch, StringArray};
+    use arrow_schema::DataType as ArrowDataType;
+    use arrow_schema::Field;
+    use arrow_schema::Schema as ArrowSchema;
+    use serde_json::json;
+    use url::Url;
+
+    #[test]
+    fn test_write_json_file() -> DeltaResult<()> {
+        let test_dir = tempfile::tempdir().unwrap();
+        let path = test_dir.path().join("00000000000000000001.json");
+        let handler = SyncJsonHandler;
+
+        let schema = Arc::new(ArrowSchema::new(vec![Field::new(
+            "dog",
+            ArrowDataType::Utf8,
+            true,
+        )]));
+        let data = RecordBatch::try_new(
+            schema.clone(),
+            vec![Arc::new(StringArray::from(vec!["remi", "wilson"]))],
+        )?;
+        let data: Box<dyn EngineData> = Box::new(ArrowEngineData::new(data));
+        let empty: Box<dyn EngineData> =
+            Box::new(ArrowEngineData::new(RecordBatch::new_empty(schema)));
+
+        let url = Url::from_file_path(path.clone()).unwrap();
+        handler
+            .write_json_file(&url, Box::new(std::iter::once(data)), false)
+            .expect("write json file");
+        assert!(matches!(
+            handler.write_json_file(&url, Box::new(std::iter::once(empty)), false),
+            Err(Error::FileAlreadyExists(_))
+        ));
+
+        let file = std::fs::read_to_string(path)?;
+        let json: Vec<_> = serde_json::Deserializer::from_str(&file)
+            .into_iter::<serde_json::Value>()
+            .flatten()
+            .collect();
+        assert_eq!(
+            json,
+            vec![json!({"dog": "remi"}), json!({"dog": "wilson"}),]
+        );
+
+        Ok(())
+    }
 }

kernel/src/error.rs

@@ -159,6 +159,18 @@ pub enum Error {
     /// Unable to parse the name of a log path
     #[error("Invalid log path: {0}")]
     InvalidLogPath(String),
+
+    /// Invalid commit info passed to the transaction
+    #[error("Invalid commit info: {0}")]
+    InvalidCommitInfo(String),
+
+    /// Commit info was not passed to the transaction
+    #[error("Missing commit info")]
+    MissingCommitInfo,
+
+    /// The file already exists at the path, prohibiting a non-overwrite write
+    #[error("File already exists: {0}")]
+    FileAlreadyExists(String),
 }
 
 // Convenience constructors for Error types that take a String argument