[python-package] Allow to pass Arrow table with boolean columns to dataset

include/LightGBM/arrow.h

@@ -84,6 +84,10 @@ class ArrowChunkedArray {
   const ArrowSchema* schema_;
   /* List of length `n + 1` for `n` chunks containing the offsets for each chunk. */
   std::vector<int64_t> chunk_offsets_;
+  /* Indicator whether this chunked array needs to call the arrays' release callbacks.
+     NOTE: This is MUST only be set to `true` if this chunked array is not part of a
+           `ArrowTable` as children arrays may not be released by the consumer (see below). */
+  const bool releases_arrow_;
 
   inline void construct_chunk_offsets() {
     chunk_offsets_.reserve(chunks_.size() + 1);
@@ -100,7 +104,8 @@ class ArrowChunkedArray {
    * @param chunks A list with the chunks.
    * @param schema The schema for all chunks.
    */
-  inline ArrowChunkedArray(std::vector<const ArrowArray*> chunks, const ArrowSchema* schema) {
+  inline ArrowChunkedArray(std::vector<const ArrowArray*> chunks, const ArrowSchema* schema)
+      : releases_arrow_(false) {
     chunks_ = chunks;
     schema_ = schema;
     construct_chunk_offsets();
@@ -113,9 +118,9 @@ class ArrowChunkedArray {
    * @param chunks A C-style array containing the chunks.
    * @param schema The schema for all chunks.
    */
-  inline ArrowChunkedArray(int64_t n_chunks,
-                           const struct ArrowArray* chunks,
-                           const struct ArrowSchema* schema) {
+  inline ArrowChunkedArray(int64_t n_chunks, const struct ArrowArray* chunks,
+                           const struct ArrowSchema* schema)
+      : releases_arrow_(true) {
     chunks_.reserve(n_chunks);
     for (auto k = 0; k < n_chunks; ++k) {
       if (chunks[k].length == 0) continue;
@@ -125,6 +130,21 @@ class ArrowChunkedArray {
     construct_chunk_offsets();
   }
 
+  ~ArrowChunkedArray() {
+    if (!releases_arrow_) {
+      return;
+    }
+    for (size_t i = 0; i < chunks_.size(); ++i) {
+      auto chunk = chunks_[i];
+      if (chunk->release) {
+        chunk->release(const_cast<ArrowArray*>(chunk));
+      }
+    }
+    if (schema_->release) {
+      schema_->release(const_cast<ArrowSchema*>(schema_));
+    }
+  }
+
   /**
    * @brief Get the length of the chunked array.
    * This method returns the cumulative length of all chunks.
@@ -219,7 +239,7 @@ class ArrowTable {
    * @param chunks A C-style array containing the chunks.
    * @param schema The schema for all chunks.
    */
-  inline ArrowTable(int64_t n_chunks, const ArrowArray *chunks, const ArrowSchema *schema)
+  inline ArrowTable(int64_t n_chunks, const ArrowArray* chunks, const ArrowSchema* schema)
       : n_chunks_(n_chunks), chunks_ptr_(chunks), schema_ptr_(schema) {
     columns_.reserve(schema->n_children);
     for (int64_t j = 0; j < schema->n_children; ++j) {
@@ -236,7 +256,8 @@ class ArrowTable {
   ~ArrowTable() {
     // As consumer of the Arrow array, the Arrow table must release all Arrow arrays it receives
     // as well as the schema. As per the specification, children arrays are released by the
-    // producer. See: https://arrow.apache.org/docs/format/CDataInterface.html#release-callback-semantics-for-consumers
+    // producer. See:
+    // https://arrow.apache.org/docs/format/CDataInterface.html#release-callback-semantics-for-consumers
     for (int64_t i = 0; i < n_chunks_; ++i) {
       auto chunk = &chunks_ptr_[i];
       if (chunk->release) {

include/LightGBM/arrow.tpp

@@ -31,8 +31,7 @@ inline ArrowChunkedArray::Iterator<T> ArrowChunkedArray::end() const {
 /* ---------------------------------- ITERATOR IMPLEMENTATION ---------------------------------- */
 
 template <typename T>
-ArrowChunkedArray::Iterator<T>::Iterator(const ArrowChunkedArray& array,
-                                         getter_fn get,
+ArrowChunkedArray::Iterator<T>::Iterator(const ArrowChunkedArray& array, getter_fn get,
                                          int64_t ptr_chunk)
     : array_(array), get_(get), ptr_chunk_(ptr_chunk) {
   this->ptr_offset_ = 0;
@@ -41,7 +40,7 @@ ArrowChunkedArray::Iterator<T>::Iterator(const ArrowChunkedArray& array,
 template <typename T>
 T ArrowChunkedArray::Iterator<T>::operator*() const {
   auto chunk = array_.chunks_[ptr_chunk_];
-  return static_cast<T>(get_(chunk, ptr_offset_));
+  return get_(chunk, ptr_offset_);
 }
 
 template <typename T>
@@ -54,7 +53,7 @@ T ArrowChunkedArray::Iterator<T>::operator[](I idx) const {
   auto chunk = array_.chunks_[chunk_idx];
 
   auto ptr_offset = static_cast<int64_t>(idx) - array_.chunk_offsets_[chunk_idx];
-  return static_cast<T>(get_(chunk, ptr_offset));
+  return get_(chunk, ptr_offset);
 }
 
 template <typename T>
@@ -147,11 +146,28 @@ struct ArrayIndexAccessor {
     if (validity == nullptr || (validity[buffer_idx / 8] & (1 << (buffer_idx % 8)))) {
       // In case the index is valid, we take it from the data buffer
       auto data = static_cast<const T*>(array->buffers[1]);
-      return static_cast<double>(data[buffer_idx]);
+      return static_cast<V>(data[buffer_idx]);
     }
 
     // In case the index is not valid, we return a default value
-    return arrow_primitive_missing_value<T>();
+    return arrow_primitive_missing_value<V>();
+  }
+};
+
+template <typename V>
+struct ArrayIndexAccessor<bool, V> {
+  V operator()(const ArrowArray* array, size_t idx) {
+    // Custom implementation for booleans as values are bit-packed:
+    // https://arrow.apache.org/docs/cpp/api/datatype.html#_CPPv4N5arrow4Type4type4BOOLE
+    auto buffer_idx = idx + array->offset;
+    auto validity = static_cast<const char*>(array->buffers[0]);
+    if (validity == nullptr || (validity[buffer_idx / 8] & (1 << (buffer_idx % 8)))) {
+      // In case the index is valid, we have to take the appropriate bit from the buffer
+      auto data = static_cast<const char*>(array->buffers[1]);
+      auto value = (data[buffer_idx / 8] & (1 << (buffer_idx % 8))) >> (buffer_idx % 8);
+      return static_cast<V>(value);
+    }
+    return arrow_primitive_missing_value<V>();
   }
 };
 
@@ -180,6 +196,8 @@ std::function<T(const ArrowArray*, size_t)> get_index_accessor(const char* dtype
       return ArrayIndexAccessor<float, T>();
     case 'g':
       return ArrayIndexAccessor<double, T>();
+    case 'b':
+      return ArrayIndexAccessor<bool, T>();
     default:
       throw std::invalid_argument("unsupported Arrow datatype");
   }

python-package/lightgbm/basic.py

@@ -22,6 +22,7 @@
     PANDAS_INSTALLED,
     PYARROW_INSTALLED,
     arrow_cffi,
+    arrow_is_boolean,
     arrow_is_floating,
     arrow_is_integer,
     concat,
@@ -1688,7 +1689,7 @@ def __pred_for_pyarrow_table(
             raise LightGBMError("Cannot predict from Arrow without `pyarrow` installed.")
 
         # Check that the input is valid: we only handle numbers (for now)
-        if not all(arrow_is_integer(t) or arrow_is_floating(t) for t in table.schema.types):
+        if not all(arrow_is_integer(t) or arrow_is_floating(t) or arrow_is_boolean(t) for t in table.schema.types):
             raise ValueError("Arrow table may only have integer or floating point datatypes")
 
         # Prepare prediction output array
@@ -2435,7 +2436,7 @@ def __init_from_pyarrow_table(
             raise LightGBMError("Cannot init dataframe from Arrow without `pyarrow` installed.")
 
         # Check that the input is valid: we only handle numbers (for now)
-        if not all(arrow_is_integer(t) or arrow_is_floating(t) for t in table.schema.types):
+        if not all(arrow_is_integer(t) or arrow_is_floating(t) or arrow_is_boolean(t) for t in table.schema.types):
             raise ValueError("Arrow table may only have integer or floating point datatypes")
 
         # Export Arrow table to C

python-package/lightgbm/compat.py

@@ -222,6 +222,7 @@ def __init__(self, *args: Any, **kwargs: Any):
     from pyarrow import Table as pa_Table
     from pyarrow import chunked_array as pa_chunked_array
     from pyarrow.cffi import ffi as arrow_cffi
+    from pyarrow.types import is_boolean as arrow_is_boolean
     from pyarrow.types import is_floating as arrow_is_floating
     from pyarrow.types import is_integer as arrow_is_integer
 
@@ -265,6 +266,7 @@ class pa_compute:  # type: ignore
         equal = None
 
     pa_chunked_array = None
+    arrow_is_boolean = None
     arrow_is_integer = None
     arrow_is_floating = None