feat: Implement LazyFrame.sink_ndjson

crates/polars-io/src/json/mod.rs

@@ -71,6 +71,7 @@ use polars_core::error::to_compute_err;
 use polars_core::prelude::*;
 use polars_core::utils::try_get_supertype;
 use polars_json::json::infer;
+use polars_json::json::write::FallibleStreamingIterator;
 use simd_json::BorrowedValue;
 
 use crate::mmap::{MmapBytesReader, ReaderBytes};
@@ -153,6 +154,34 @@ where
     }
 }
 
+pub struct BatchedWriter<W: Write> {
+    writer: W,
+}
+
+impl<W> BatchedWriter<W>
+where
+    W: Write,
+{
+    pub fn new(writer: W) -> Self {
+        BatchedWriter { writer }
+    }
+    /// Write a batch to the json writer.
+    ///
+    /// # Panics
+    /// The caller must ensure the chunks in the given [`DataFrame`] are aligned.
+    pub fn write_batch(&mut self, df: &DataFrame) -> PolarsResult<()> {
+        let fields = df.iter().map(|s| s.field().to_arrow()).collect::<Vec<_>>();
+        let chunks = df.iter_chunks();
+        let batches =
+            chunks.map(|chunk| Ok(Box::new(chunk_to_struct(chunk, fields.clone())) as ArrayRef));
+        let mut serializer = polars_json::ndjson::write::Serializer::new(batches, vec![]);
+        while let Some(block) = serializer.next()? {
+            self.writer.write_all(block)?;
+        }
+        Ok(())
+    }
+}
+
 /// Reads JSON in one of the formats in [`JsonFormat`] into a DataFrame.
 #[must_use]
 pub struct JsonReader<'a, R>

crates/polars-lazy/Cargo.toml

@@ -47,7 +47,7 @@ async = [
 cloud = ["async", "polars-pipe?/cloud", "polars-plan/cloud", "tokio", "futures"]
 cloud_write = ["cloud"]
 ipc = ["polars-io/ipc", "polars-plan/ipc", "polars-pipe?/ipc"]
-json = ["polars-io/json", "polars-plan/json", "polars-json"]
+json = ["polars-io/json", "polars-plan/json", "polars-json", "polars-pipe/json"]
 csv = ["polars-io/csv", "polars-plan/csv", "polars-pipe?/csv"]
 temporal = ["dtype-datetime", "dtype-date", "dtype-time", "dtype-duration", "polars-plan/temporal"]
 # debugging purposes

crates/polars-lazy/src/frame/mod.rs

@@ -7,7 +7,12 @@ mod err;
 pub mod pivot;
 
 use std::borrow::Cow;
-#[cfg(any(feature = "parquet", feature = "ipc", feature = "csv"))]
+#[cfg(any(
+    feature = "parquet",
+    feature = "ipc",
+    feature = "csv",
+    feature = "json"
+))]
 use std::path::PathBuf;
 use std::sync::Arc;
 
@@ -27,7 +32,12 @@ use polars_core::prelude::*;
 use polars_io::RowCount;
 pub use polars_plan::frame::{AllowedOptimizations, OptState};
 use polars_plan::global::FETCH_ROWS;
-#[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+#[cfg(any(
+    feature = "ipc",
+    feature = "parquet",
+    feature = "csv",
+    feature = "json"
+))]
 use polars_plan::logical_plan::collect_fingerprints;
 use polars_plan::logical_plan::optimize;
 use polars_plan::utils::expr_output_name;
@@ -596,13 +606,23 @@ impl LazyFrame {
             self.optimize_with_scratch(&mut lp_arena, &mut expr_arena, &mut scratch, false)?;
 
         let finger_prints = if file_caching {
-            #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+            #[cfg(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            ))]
             {
                 let mut fps = Vec::with_capacity(8);
                 collect_fingerprints(lp_top, &mut fps, &lp_arena, &expr_arena);
                 Some(fps)
             }
-            #[cfg(not(any(feature = "ipc", feature = "parquet", feature = "csv")))]
+            #[cfg(not(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            )))]
             {
                 None
             }
@@ -669,23 +689,14 @@ impl LazyFrame {
     /// into memory. This methods will return an error if the query cannot be completely done in a
     /// streaming fashion.
     #[cfg(feature = "parquet")]
-    pub fn sink_parquet(mut self, path: PathBuf, options: ParquetWriteOptions) -> PolarsResult<()> {
-        self.opt_state.streaming = true;
-        self.logical_plan = LogicalPlan::Sink {
-            input: Box::new(self.logical_plan),
-            payload: SinkType::File {
+    pub fn sink_parquet(self, path: PathBuf, options: ParquetWriteOptions) -> PolarsResult<()> {
+        self.sink(
+            SinkType::File {
                 path: Arc::new(path),
                 file_type: FileType::Parquet(options),
             },
-        };
-        let (mut state, mut physical_plan, is_streaming) = self.prepare_collect(true)?;
-        polars_ensure!(
-            is_streaming,
-            ComputeError: "cannot run the whole query in a streaming order; \
-            use `collect().write_parquet()` instead"
-        );
-        let _ = physical_plan.execute(&mut state)?;
-        Ok(())
+            "collect().write_parquet()",
+        )
     }
 
     /// Stream a query result into a parquet file on an ObjectStore-compatible cloud service. This is useful if the final result doesn't fit
@@ -694,70 +705,81 @@ impl LazyFrame {
     /// streaming fashion.
     #[cfg(all(feature = "cloud_write", feature = "parquet"))]
     pub fn sink_parquet_cloud(
-        mut self,
+        self,
         uri: String,
         cloud_options: Option<polars_io::cloud::CloudOptions>,
         parquet_options: ParquetWriteOptions,
     ) -> PolarsResult<()> {
-        self.opt_state.streaming = true;
-        self.logical_plan = LogicalPlan::Sink {
-            input: Box::new(self.logical_plan),
-            payload: SinkType::Cloud {
+        self.sink(
+            SinkType::Cloud {
                 uri: Arc::new(uri),
                 cloud_options,
                 file_type: FileType::Parquet(parquet_options),
             },
-        };
-        let (mut state, mut physical_plan, is_streaming) = self.prepare_collect(true)?;
-        polars_ensure!(
-            is_streaming,
-            ComputeError: "cannot run the whole query in a streaming order"
-        );
-        let _ = physical_plan.execute(&mut state)?;
-        Ok(())
+            "collect().write_parquet()",
+        )
     }
 
     /// Stream a query result into an ipc/arrow file. This is useful if the final result doesn't fit
     /// into memory. This methods will return an error if the query cannot be completely done in a
     /// streaming fashion.
     #[cfg(feature = "ipc")]
-    pub fn sink_ipc(mut self, path: PathBuf, options: IpcWriterOptions) -> PolarsResult<()> {
-        self.opt_state.streaming = true;
-        self.logical_plan = LogicalPlan::Sink {
-            input: Box::new(self.logical_plan),
-            payload: SinkType::File {
+    pub fn sink_ipc(self, path: PathBuf, options: IpcWriterOptions) -> PolarsResult<()> {
+        self.sink(
+            SinkType::File {
                 path: Arc::new(path),
                 file_type: FileType::Ipc(options),
             },
-        };
-        let (mut state, mut physical_plan, is_streaming) = self.prepare_collect(true)?;
-        polars_ensure!(
-            is_streaming,
-            ComputeError: "cannot run the whole query in a streaming order; \
-            use `collect().write_ipc()` instead"
-        );
-        let _ = physical_plan.execute(&mut state)?;
-        Ok(())
+            "collect().write_ipc()",
+        )
     }
 
     /// Stream a query result into an csv file. This is useful if the final result doesn't fit
     /// into memory. This methods will return an error if the query cannot be completely done in a
     /// streaming fashion.
     #[cfg(feature = "csv")]
-    pub fn sink_csv(mut self, path: PathBuf, options: CsvWriterOptions) -> PolarsResult<()> {
-        self.opt_state.streaming = true;
-        self.logical_plan = LogicalPlan::Sink {
-            input: Box::new(self.logical_plan),
-            payload: SinkType::File {
+    pub fn sink_csv(self, path: PathBuf, options: CsvWriterOptions) -> PolarsResult<()> {
+        self.sink(
+            SinkType::File {
                 path: Arc::new(path),
                 file_type: FileType::Csv(options),
             },
+            "collect().write_csv()",
+        )
+    }
+
+    /// Stream a query result into a json file. This is useful if the final result doesn't fit
+    /// into memory. This methods will return an error if the query cannot be completely done in a
+    /// streaming fashion.
+    #[cfg(feature = "json")]
+    pub fn sink_json(self, path: PathBuf, options: JsonWriterOptions) -> PolarsResult<()> {
+        self.sink(
+            SinkType::File {
+                path: Arc::new(path),
+                file_type: FileType::Json(options),
+            },
+            "collect().write_ndjson()` or `collect().write_json()",
+        )
+    }
+
+    #[cfg(any(
+        feature = "ipc",
+        feature = "parquet",
+        feature = "cloud_write",
+        feature = "csv",
+        feature = "json",
+    ))]
+    fn sink(mut self, payload: SinkType, msg_alternative: &str) -> Result<(), PolarsError> {
+        self.opt_state.streaming = true;
+        self.logical_plan = LogicalPlan::Sink {
+            input: Box::new(self.logical_plan),
+            payload,
         };
         let (mut state, mut physical_plan, is_streaming) = self.prepare_collect(true)?;
         polars_ensure!(
             is_streaming,
-            ComputeError: "cannot run the whole query in a streaming order; \
-            use `collect().write_csv()` instead"
+            ComputeError: format!("cannot run the whole query in a streaming order; \
+            use `{msg_alternative}` instead", msg_alternative=msg_alternative)
         );
         let _ = physical_plan.execute(&mut state)?;
         Ok(())

crates/polars-lazy/src/physical_plan/file_cache.rs

@@ -1,7 +1,12 @@
 use std::sync::Mutex;
 
 use polars_core::prelude::*;
-#[cfg(any(feature = "parquet", feature = "csv", feature = "ipc"))]
+#[cfg(any(
+    feature = "parquet",
+    feature = "csv",
+    feature = "ipc",
+    feature = "json"
+))]
 use polars_plan::logical_plan::FileFingerPrint;
 
 use crate::prelude::*;

crates/polars-lazy/src/physical_plan/mod.rs

@@ -2,7 +2,12 @@ pub mod executors;
 #[cfg(any(feature = "list_eval", feature = "pivot"))]
 pub(crate) mod exotic;
 pub mod expressions;
-#[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+#[cfg(any(
+    feature = "ipc",
+    feature = "parquet",
+    feature = "csv",
+    feature = "json"
+))]
 mod file_cache;
 mod node_timer;
 pub mod planner;

crates/polars-lazy/src/physical_plan/state.rs

@@ -8,10 +8,20 @@ use polars_core::config::verbose;
 use polars_core::frame::group_by::GroupsProxy;
 use polars_core::prelude::*;
 use polars_ops::prelude::ChunkJoinOptIds;
-#[cfg(any(feature = "parquet", feature = "csv", feature = "ipc"))]
+#[cfg(any(
+    feature = "parquet",
+    feature = "csv",
+    feature = "ipc",
+    feature = "json"
+))]
 use polars_plan::logical_plan::FileFingerPrint;
 
-#[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+#[cfg(any(
+    feature = "ipc",
+    feature = "parquet",
+    feature = "csv",
+    feature = "json"
+))]
 use super::file_cache::FileCache;
 use crate::physical_plan::node_timer::NodeTimer;
 
@@ -65,7 +75,12 @@ pub struct ExecutionState {
     // cached by a `.cache` call and kept in memory for the duration of the plan.
     df_cache: Arc<Mutex<PlHashMap<usize, Arc<OnceCell<DataFrame>>>>>,
     // cache file reads until all branches got there file, then we delete it
-    #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+    #[cfg(any(
+        feature = "ipc",
+        feature = "parquet",
+        feature = "csv",
+        feature = "json"
+    ))]
     pub(crate) file_cache: FileCache,
     pub(super) schema_cache: RwLock<Option<SchemaRef>>,
     /// Used by Window Expression to prevent redundant grouping
@@ -110,7 +125,12 @@ impl ExecutionState {
     pub(super) fn split(&self) -> Self {
         Self {
             df_cache: self.df_cache.clone(),
-            #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+            #[cfg(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            ))]
             file_cache: self.file_cache.clone(),
             schema_cache: Default::default(),
             group_tuples: Default::default(),
@@ -126,7 +146,12 @@ impl ExecutionState {
     pub(super) fn clone(&self) -> Self {
         Self {
             df_cache: self.df_cache.clone(),
-            #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+            #[cfg(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            ))]
             file_cache: self.file_cache.clone(),
             schema_cache: self.schema_cache.read().unwrap().clone().into(),
             group_tuples: self.group_tuples.clone(),
@@ -138,16 +163,31 @@ impl ExecutionState {
         }
     }
 
-    #[cfg(not(any(feature = "parquet", feature = "csv", feature = "ipc")))]
+    #[cfg(not(any(
+        feature = "parquet",
+        feature = "csv",
+        feature = "ipc",
+        feature = "json"
+    )))]
     pub(crate) fn with_finger_prints(_finger_prints: Option<usize>) -> Self {
         Self::new()
     }
-    #[cfg(any(feature = "parquet", feature = "csv", feature = "ipc"))]
+    #[cfg(any(
+        feature = "parquet",
+        feature = "csv",
+        feature = "ipc",
+        feature = "json"
+    ))]
     pub(crate) fn with_finger_prints(finger_prints: Option<Vec<FileFingerPrint>>) -> Self {
         Self {
             df_cache: Arc::new(Mutex::new(PlHashMap::default())),
             schema_cache: Default::default(),
-            #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+            #[cfg(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            ))]
             file_cache: FileCache::new(finger_prints),
             group_tuples: Arc::new(RwLock::new(PlHashMap::default())),
             join_tuples: Arc::new(Mutex::new(PlHashMap::default())),
@@ -166,7 +206,12 @@ impl ExecutionState {
         Self {
             df_cache: Default::default(),
             schema_cache: Default::default(),
-            #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
+            #[cfg(any(
+                feature = "ipc",
+                feature = "parquet",
+                feature = "csv",
+                feature = "json"
+            ))]
             file_cache: FileCache::new(None),
             group_tuples: Default::default(),
             join_tuples: Default::default(),