pitrou commented on a change in pull request #10991:
URL: https://github.com/apache/arrow/pull/10991#discussion_r707564352
##########
File path: python/pyarrow/_dataset.pyx
##########
@@ -53,6 +53,26 @@ def _forbid_instantiation(klass, subclasses_instead=True):
raise TypeError(msg)
+_orc_fileformat = None
+_orc_imported = False
+
+
+def _get_orc_filesystem():
+ """
+ Import OrcFileSystem on first usage (to avoid circular import issue
+ when `pyarrow._dataset_orc` would be imported first)
+ """
+ global _orc_fileformat
+ global _orc_imported
+ if not _orc_imported:
Review comment:
`_orc_imported` is never set?
##########
File path: python/pyarrow/_dataset.pyx
##########
@@ -53,6 +53,26 @@ def _forbid_instantiation(klass, subclasses_instead=True):
raise TypeError(msg)
+_orc_fileformat = None
+_orc_imported = False
+
+
+def _get_orc_filesystem():
Review comment:
"file format" rather than "filesystem", no?
##########
File path: cpp/src/arrow/dataset/file_orc.cc
##########
@@ -0,0 +1,185 @@
+// 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.
+
+#include "arrow/dataset/file_orc.h"
+
+#include <memory>
+
+#include "arrow/adapters/orc/adapter.h"
+#include "arrow/dataset/dataset_internal.h"
+#include "arrow/dataset/file_base.h"
+#include "arrow/dataset/scanner.h"
+#include "arrow/util/checked_cast.h"
+#include "arrow/util/iterator.h"
+#include "arrow/util/logging.h"
+
+namespace arrow {
+
+using internal::checked_pointer_cast;
+
+namespace dataset {
+
+namespace {
+
+static inline Result<std::unique_ptr<arrow::adapters::orc::ORCFileReader>>
OpenReader(
+ const FileSource& source,
+ const std::shared_ptr<ScanOptions>& scan_options = nullptr) {
+ ARROW_ASSIGN_OR_RAISE(auto input, source.Open());
+
+ arrow::MemoryPool* pool;
+ if (scan_options) {
+ pool = scan_options->pool;
+ } else {
+ pool = default_memory_pool();
+ }
+
+ std::unique_ptr<arrow::adapters::orc::ORCFileReader> reader;
+ auto status =
+ arrow::adapters::orc::ORCFileReader::Open(std::move(input), pool,
&reader);
+ if (!status.ok()) {
+ return status.WithMessage("Could not open ORC input source '",
source.path(),
+ "': ", status.message());
+ }
+ return reader;
+}
+
+/// \brief A ScanTask backed by an ORC file.
+class OrcScanTask : public ScanTask {
+ public:
+ OrcScanTask(std::shared_ptr<FileFragment> fragment,
+ std::shared_ptr<ScanOptions> options)
+ : ScanTask(std::move(options), fragment), source_(fragment->source()) {}
+
+ Result<RecordBatchIterator> Execute() override {
+ struct Impl {
+ static Result<RecordBatchIterator> Make(const FileSource& source,
+ const FileFormat& format,
+ const ScanOptions& scan_options)
{
+ ARROW_ASSIGN_OR_RAISE(
+ auto reader, OpenReader(source,
std::make_shared<ScanOptions>(scan_options)));
+ int num_stripes = reader->NumberOfStripes();
+ return RecordBatchIterator(Impl{std::move(reader), 0, num_stripes});
+ }
+
+ Result<std::shared_ptr<RecordBatch>> Next() {
+ if (i_ == num_stripes_) {
+ return nullptr;
+ }
+ std::shared_ptr<RecordBatch> batch;
+ // TODO (https://issues.apache.org/jira/browse/ARROW-13797)
+ // determine included fields from options_->MaterializedFields() to
+ // optimize the column selection (see _column_index_lookup in python
+ // orc.py for custom logic)
+ // std::vector<int> included_fields;
+ // TODO pass scan_options_->batch_size
+ reader_->ReadStripe(i_++, &batch);
+ return batch;
+ }
+
+ std::unique_ptr<arrow::adapters::orc::ORCFileReader> reader_;
+ int i_;
+ int num_stripes_;
+ };
+
+ return Impl::Make(source_,
*checked_pointer_cast<FileFragment>(fragment_)->format(),
+ *options_);
+ }
+
+ private:
+ FileSource source_;
+};
+
+class OrcScanTaskIterator {
+ public:
+ static Result<ScanTaskIterator> Make(std::shared_ptr<ScanOptions> options,
+ std::shared_ptr<FileFragment> fragment)
{
+ return ScanTaskIterator(OrcScanTaskIterator(std::move(options),
std::move(fragment)));
+ }
+
+ Result<std::shared_ptr<ScanTask>> Next() {
+ if (once_) {
+ // Iteration is done.
+ return nullptr;
+ }
+
+ once_ = true;
+ return std::shared_ptr<ScanTask>(new OrcScanTask(fragment_, options_));
+ }
+
+ private:
+ OrcScanTaskIterator(std::shared_ptr<ScanOptions> options,
+ std::shared_ptr<FileFragment> fragment)
+ : options_(std::move(options)), fragment_(std::move(fragment)) {}
+
+ bool once_ = false;
+ std::shared_ptr<ScanOptions> options_;
+ std::shared_ptr<FileFragment> fragment_;
+};
+
+} // namespace
+
+Result<bool> OrcFileFormat::IsSupported(const FileSource& source) const {
+ RETURN_NOT_OK(source.Open().status());
+ return OpenReader(source).ok();
+}
+
+Result<std::shared_ptr<Schema>> OrcFileFormat::Inspect(const FileSource&
source) const {
+ ARROW_ASSIGN_OR_RAISE(auto reader, OpenReader(source));
+ std::shared_ptr<Schema> schema;
+ RETURN_NOT_OK(reader->ReadSchema(&schema));
+ return schema;
+}
+
+Result<ScanTaskIterator> OrcFileFormat::ScanFile(
+ const std::shared_ptr<ScanOptions>& options,
+ const std::shared_ptr<FileFragment>& fragment) const {
+ return OrcScanTaskIterator::Make(options, fragment);
+}
+
+Future<util::optional<int64_t>> OrcFileFormat::CountRows(
+ const std::shared_ptr<FileFragment>& file, compute::Expression predicate,
+ const std::shared_ptr<ScanOptions>& options) {
+ if (ExpressionHasFieldRefs(predicate)) {
+ return Future<util::optional<int64_t>>::MakeFinished(util::nullopt);
+ }
+ auto self = checked_pointer_cast<OrcFileFormat>(shared_from_this());
+ return DeferNotOk(options->io_context.executor()->Submit(
+ [self, file]() -> Result<util::optional<int64_t>> {
+ ARROW_ASSIGN_OR_RAISE(auto reader, OpenReader(file->source()));
+ return reader->NumberOfRows();
+ }));
+}
+
+// //
+// // IpcFileWriter, IpcFileWriteOptions
+// //
Review comment:
Ping on this :-)
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