Implement PyArrow Dataset TableProvider

Cargo.toml

@@ -39,6 +39,8 @@ datafusion-expr = { version = "^8.0.0" }
 datafusion-common = { version = "^8.0.0", features = ["pyarrow"] }
 uuid = { version = "0.8", features = ["v4"] }
 mimalloc = { version = "*", optional = true, default-features = false }
+async-trait = "0.1"
+futures = "0.3"
 
 [lib]
 name = "datafusion_python"

datafusion/tests/test_context.py

@@ -16,6 +16,7 @@
 # under the License.
 
 import pyarrow as pa
+import pyarrow.dataset as ds
 
 
 def test_register_record_batches(ctx):
@@ -72,3 +73,35 @@ def test_deregister_table(ctx, database):
 
     ctx.deregister_table("csv")
     assert public.names() == {"csv1", "csv2"}
+
+def test_register_dataset(ctx):
+    # create a RecordBatch and register it as a pyarrow.dataset.Dataset
+    batch = pa.RecordBatch.from_arrays(
+        [pa.array([1, 2, 3]), pa.array([4, 5, 6])],
+        names=["a", "b"],
+    )
+    dataset = ds.dataset([batch])
+    ctx.register_dataset("t", dataset)
+
+    assert ctx.tables() == {"t"}
+
+    result = ctx.sql("SELECT a+b, a-b FROM t").collect()
+
+    assert result[0].column(0) == pa.array([5, 7, 9])
+    assert result[0].column(1) == pa.array([-3, -3, -3])
+
+def test_dataset_filter(ctx):
+    # create a RecordBatch and register it as a pyarrow.dataset.Dataset
+    batch = pa.RecordBatch.from_arrays(
+        [pa.array([1, 2, 3]), pa.array([4, 5, 6])],
+        names=["a", "b"],
+    )
+    dataset = ds.dataset([batch])
+    ctx.register_dataset("t", dataset)
+
+    assert ctx.tables() == {"t"}
+
+    result = ctx.sql("SELECT a+b, a-b FROM t WHERE a BETWEEN 2 and 3 AND b > 5").collect()
+
+    assert result[0].column(0) == pa.array([9])
+    assert result[0].column(1) == pa.array([-3])

datafusion/tests/test_sql.py

@@ -17,6 +17,7 @@
 
 import numpy as np
 import pyarrow as pa
+import pyarrow.dataset as ds
 import pytest
 
 from datafusion import udf
@@ -121,6 +122,17 @@ def test_register_parquet_partitioned(ctx, tmp_path):
     rd = result.to_pydict()
     assert dict(zip(rd["grp"], rd["cnt"])) == {"a": 3, "b": 1}
 
+def test_register_dataset(ctx, tmp_path):
+    path = helpers.write_parquet(tmp_path / "a.parquet", helpers.data())
+    dataset = ds.dataset(path, format="parquet")
+
+    ctx.register_dataset("t", dataset)
+    assert ctx.tables() == {"t"}
+
+    result = ctx.sql("SELECT COUNT(a) AS cnt FROM t").collect()
+    result = pa.Table.from_batches(result)
+    assert result.to_pydict() == {"cnt": [100]}
+
 
 def test_execute(ctx, tmp_path):
     data = [1, 1, 2, 2, 3, 11, 12]

src/context.rs

@@ -25,12 +25,14 @@ use pyo3::prelude::*;
 
 use datafusion::arrow::datatypes::Schema;
 use datafusion::arrow::record_batch::RecordBatch;
+use datafusion::datasource::datasource::TableProvider;
 use datafusion::datasource::MemTable;
 use datafusion::execution::context::SessionContext;
 use datafusion::prelude::{CsvReadOptions, ParquetReadOptions};
 
 use crate::catalog::{PyCatalog, PyTable};
 use crate::dataframe::PyDataFrame;
+use crate::dataset::Dataset;
 use crate::errors::DataFusionError;
 use crate::udf::PyScalarUDF;
 use crate::utils::wait_for_future;
@@ -173,6 +175,17 @@ impl PySessionContext {
         Ok(())
     }
 
+    // Registers a PyArrow.Dataset
+    fn register_dataset(&self, name: &str, dataset: &PyAny, py: Python) -> PyResult<()> {
+        let table: Arc<dyn TableProvider> = Arc::new(Dataset::new(dataset, py)?);
+
+        self.ctx
+            .register_table(name, table)
+            .map_err(DataFusionError::from)?;
+
+        Ok(())
+    }
+
     fn register_udf(&mut self, udf: PyScalarUDF) -> PyResult<()> {
         self.ctx.register_udf(udf.function);
         Ok(())

src/dataset.rs

@@ -0,0 +1,116 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use pyo3::exceptions::PyValueError;
+/// Implements a Datafusion TableProvider that delegates to a PyArrow Dataset
+/// This allows us to use PyArrow Datasets as Datafusion tables while pushing down projections and filters
+use pyo3::prelude::*;
+use pyo3::types::PyType;
+
+use std::any::Any;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+
+use datafusion::arrow::datatypes::SchemaRef;
+use datafusion::datasource::datasource::TableProviderFilterPushDown;
+use datafusion::datasource::{TableProvider, TableType};
+use datafusion::error::{DataFusionError, Result as DFResult};
+use datafusion::logical_plan::*;
+use datafusion::physical_plan::ExecutionPlan;
+
+use crate::dataset_exec::DatasetExec;
+use crate::pyarrow_filter_expression::PyArrowFilterExpression;
+
+// Wraps a pyarrow.dataset.Dataset class and implements a Datafusion TableProvider around it
+#[derive(Debug, Clone)]
+pub(crate) struct Dataset {
+    dataset: PyObject,
+}
+
+impl Dataset {
+    // Creates a Python PyArrow.Dataset
+    pub fn new(dataset: &PyAny, py: Python) -> PyResult<Self> {
+        // Ensure that we were passed an instance of pyarrow.dataset.Dataset
+        let ds = PyModule::import(py, "pyarrow.dataset")?;
+        let ds_type: &PyType = ds.getattr("Dataset")?.downcast()?;
+        if dataset.is_instance(ds_type)? {
+            Ok(Dataset {
+                dataset: dataset.into(),
+            })
+        } else {
+            Err(PyValueError::new_err(
+                "dataset argument must be a pyarrow.dataset.Dataset object",
+            ))
+        }
+    }
+}
+
+#[async_trait]
+impl TableProvider for Dataset {
+    /// Returns the table provider as [`Any`](std::any::Any) so that it can be
+    /// downcast to a specific implementation.
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    /// Get a reference to the schema for this table
+    fn schema(&self) -> SchemaRef {
+        Python::with_gil(|py| {
+            let dataset = self.dataset.as_ref(py);
+            // This can panic but since we checked that self.dataset is a pyarrow.dataset.Dataset it should never
+            Arc::new(dataset.getattr("schema").unwrap().extract().unwrap())
+        })
+    }
+
+    /// Get the type of this table for metadata/catalog purposes.
+    fn table_type(&self) -> TableType {
+        TableType::Base
+    }
+
+    /// Create an ExecutionPlan that will scan the table.
+    /// The table provider will be usually responsible of grouping
+    /// the source data into partitions that can be efficiently
+    /// parallelized or distributed.
+    async fn scan(
+        &self,
+        projection: &Option<Vec<usize>>,
+        filters: &[Expr],
+        // limit can be used to reduce the amount scanned
+        // from the datasource as a performance optimization.
+        // If set, it contains the amount of rows needed by the `LogicalPlan`,
+        // The datasource should return *at least* this number of rows if available.
+        _limit: Option<usize>,
+    ) -> DFResult<Arc<dyn ExecutionPlan>> {
+        Python::with_gil(|py| {
+            let plan: Arc<dyn ExecutionPlan> = Arc::new(
+                DatasetExec::new(py, self.dataset.as_ref(py), projection.clone(), filters)
+                    .map_err(|err| DataFusionError::External(Box::new(err)))?,
+            );
+            Ok(plan)
+        })
+    }
+
+    /// Tests whether the table provider can make use of a filter expression
+    /// to optimise data retrieval.
+    fn supports_filter_pushdown(&self, filter: &Expr) -> DFResult<TableProviderFilterPushDown> {
+        match PyArrowFilterExpression::try_from(filter) {
+            Ok(_) => Ok(TableProviderFilterPushDown::Exact),
+            _ => Ok(TableProviderFilterPushDown::Unsupported),
+        }
+    }
+}