[GitHub] [arrow] wjones127 commented on a diff in pull request #14018: ARROW-14161: [C++][Docs] Improve Parquet C++ docs

[GitBox <gi...@apache.org>]

wjones127 commented on code in PR #14018:
URL: https://github.com/apache/arrow/pull/14018#discussion_r1017201704


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cpp/examples/arrow/parquet_read_write.cc:
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@@ -0,0 +1,189 @@
+// 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/api.h"
+#include "arrow/io/api.h"
+#include "arrow/result.h"
+#include "arrow/util/type_fwd.h"
+#include "parquet/arrow/reader.h"
+#include "parquet/arrow/writer.h"
+
+#include <iostream>
+
+arrow::Status ReadFullFile(std::string path_to_file) {
+  // #include "arrow/io/api.h"
+  // #include "arrow/parquet/arrow/reader.h"
+
+  arrow::MemoryPool* pool = arrow::default_memory_pool();
+  std::shared_ptr<arrow::io::RandomAccessFile> input;
+  ARROW_ASSIGN_OR_RAISE(input, arrow::io::ReadableFile::Open(path_to_file));
+
+  // Open Parquet file reader
+  std::unique_ptr<parquet::arrow::FileReader> arrow_reader;
+  ARROW_RETURN_NOT_OK(parquet::arrow::OpenFile(input, pool, &arrow_reader));
+
+  // Read entire file as a single Arrow table
+  std::shared_ptr<arrow::Table> table;
+  ARROW_RETURN_NOT_OK(arrow_reader->ReadTable(&table));
+  return arrow::Status::OK();
+}
+
+arrow::Status ReadInBatches(std::string path_to_file) {
+  // #include "arrow/io/api.h"
+  // #include "arrow/parquet/arrow/reader.h"
+
+  arrow::MemoryPool* pool = arrow::default_memory_pool();
+
+  // Configure general Parquet reader settings
+  auto reader_properties = parquet::ReaderProperties(pool);
+  reader_properties.set_buffer_size(4096 * 4);
+  reader_properties.enable_buffered_stream();
+
+  // Configure Arrow-specific Parquet reader settings
+  auto arrow_reader_props = parquet::ArrowReaderProperties();
+  arrow_reader_props.set_batch_size(128 * 1024);  // default 64 * 1024
+
+  parquet::arrow::FileReaderBuilder reader_builder;
+  ARROW_RETURN_NOT_OK(
+      reader_builder.OpenFile(path_to_file, /*memory_map=*/false, reader_properties));
+  reader_builder.memory_pool(pool);
+  reader_builder.properties(arrow_reader_props);
+
+  std::unique_ptr<parquet::arrow::FileReader> arrow_reader;
+  ARROW_ASSIGN_OR_RAISE(arrow_reader, reader_builder.Build());
+
+  std::shared_ptr<::arrow::RecordBatchReader> rb_reader;
+  ARROW_RETURN_NOT_OK(arrow_reader->GetRecordBatchReader(&rb_reader));
+
+  for (arrow::Result<std::shared_ptr<arrow::RecordBatch>> maybe_batch : *rb_reader) {
+    // Operate on each batch...
+  }
+  return arrow::Status::OK();
+}
+
+arrow::Result<std::shared_ptr<arrow::Table>> GetTable() {
+  auto builder = arrow::Int32Builder();
+
+  std::shared_ptr<arrow::Array> arr_x;
+  ARROW_RETURN_NOT_OK(builder.AppendValues({1, 3, 5, 7, 1}));
+  ARROW_RETURN_NOT_OK(builder.Finish(&arr_x));
+
+  std::shared_ptr<arrow::Array> arr_y;
+  ARROW_RETURN_NOT_OK(builder.AppendValues({2, 4, 6, 8, 10}));
+  ARROW_RETURN_NOT_OK(builder.Finish(&arr_y));
+
+  auto schema = arrow::schema(
+      {arrow::field("x", arrow::int32()), arrow::field("y", arrow::int32())});
+
+  return arrow::Table::Make(schema, {arr_x, arr_y});
+}
+
+arrow::Result<std::shared_ptr<arrow::TableBatchReader>> GetRBR() {
+  ARROW_ASSIGN_OR_RAISE(std::shared_ptr<arrow::Table> table, GetTable());
+  auto reader = std::make_shared<arrow::TableBatchReader>(table);
+  reader->set_chunksize(10);
+  return reader;
+}
+
+arrow::Status WriteFullFile(std::string path_to_file) {
+  // #include "parquet/arrow/writer.h"
+  // #include "arrow/util/type_fwd.h"
+  using parquet::ArrowWriterProperties;
+  using parquet::WriterProperties;
+
+  ARROW_ASSIGN_OR_RAISE(std::shared_ptr<arrow::Table> table, GetTable());
+
+  // Choose compression
+  std::shared_ptr<WriterProperties> props =
+      WriterProperties::Builder().compression(arrow::Compression::SNAPPY)->build();
+
+  // Opt to store Arrow schema for easier reads back into Arrow
+  std::shared_ptr<ArrowWriterProperties> arrow_props =
+      ArrowWriterProperties::Builder().store_schema()->build();
+
+  std::shared_ptr<arrow::io::FileOutputStream> outfile;
+  ARROW_ASSIGN_OR_RAISE(outfile, arrow::io::FileOutputStream::Open(path_to_file));
+
+  ARROW_RETURN_NOT_OK(parquet::arrow::WriteTable(*table.get(),
+                                                 arrow::default_memory_pool(), outfile,
+                                                 /*chunk_size=*/3, props, arrow_props));
+  return arrow::Status::OK();
+}
+
+arrow::Status WriteInBatches(std::string path_to_file) {
+  // #include "parquet/arrow/writer.h"
+  // #include "arrow/util/type_fwd.h"
+  using parquet::ArrowWriterProperties;
+  using parquet::WriterProperties;
+
+  // Data is in RBR
+  std::shared_ptr<arrow::RecordBatchReader> batch_stream;
+  ARROW_ASSIGN_OR_RAISE(batch_stream, GetRBR());
+
+  // Choose compression
+  std::shared_ptr<WriterProperties> props =
+      WriterProperties::Builder().compression(arrow::Compression::SNAPPY)->build();
+
+  // Opt to store Arrow schema for easier reads back into Arrow
+  std::shared_ptr<ArrowWriterProperties> arrow_props =
+      ArrowWriterProperties::Builder().store_schema()->build();
+
+  // Create a writer
+  std::shared_ptr<arrow::io::FileOutputStream> outfile;
+  ARROW_ASSIGN_OR_RAISE(outfile, arrow::io::FileOutputStream::Open(path_to_file));
+  std::unique_ptr<parquet::arrow::FileWriter> writer;
+  ARROW_ASSIGN_OR_RAISE(
+      writer, parquet::arrow::FileWriter::Open(*batch_stream->schema().get(),
+                                               arrow::default_memory_pool(), outfile,
+                                               props, arrow_props));
+
+  // Write each batch as a row_group
+  for (arrow::Result<std::shared_ptr<arrow::RecordBatch>> maybe_batch : *batch_stream) {
+    ARROW_ASSIGN_OR_RAISE(auto batch, maybe_batch);
+    ARROW_ASSIGN_OR_RAISE(auto table,
+                          arrow::Table::FromRecordBatches(batch->schema(), {batch}));
+    ARROW_RETURN_NOT_OK(writer->WriteTable(*table.get(), batch->num_rows()));
+  }
+
+  // Write file footer and close
+  ARROW_RETURN_NOT_OK(writer->Close());
+
+  return arrow::Status::OK();
+}
+
+arrow::Status RunExamples(std::string path_to_file) {
+  ARROW_RETURN_NOT_OK(WriteFullFile(path_to_file));
+  ARROW_RETURN_NOT_OK(ReadFullFile(path_to_file));
+  ARROW_RETURN_NOT_OK(ReadInBatches(path_to_file));
+  return arrow::Status::OK();

Review Comment:
   Nope 🤦 



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