| // 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 <cassert> |
| #include <fstream> |
| #include <iostream> |
| #include <memory> |
| |
| #include <reader_writer.h> |
| |
| /* |
| * This example describes writing and reading Parquet Files in C++ and serves as a |
| * reference to the API. |
| * The file contains all the physical data types supported by Parquet. |
| * This example uses the RowGroupWriter API that supports writing RowGroups optimized for |
| *memory consumption |
| **/ |
| |
| /* Parquet is a structured columnar file format |
| * Parquet File = "Parquet data" + "Parquet Metadata" |
| * "Parquet data" is simply a vector of RowGroups. Each RowGroup is a batch of rows in a |
| * columnar layout |
| * "Parquet Metadata" contains the "file schema" and attributes of the RowGroups and their |
| * Columns |
| * "file schema" is a tree where each node is either a primitive type (leaf nodes) or a |
| * complex (nested) type (internal nodes) |
| * For specific details, please refer the format here: |
| * https://github.com/apache/parquet-format/blob/master/LogicalTypes.md |
| **/ |
| |
| constexpr int NUM_ROWS_PER_ROW_GROUP = 500; |
| const char PARQUET_FILENAME[] = "parquet_cpp_example.parquet"; |
| |
| int main(int argc, char** argv) { |
| /********************************************************************************** |
| PARQUET WRITER EXAMPLE |
| **********************************************************************************/ |
| // parquet::REQUIRED fields do not need definition and repetition level values |
| // parquet::OPTIONAL fields require only definition level values |
| // parquet::REPEATED fields require both definition and repetition level values |
| try { |
| // Create a local file output stream instance. |
| using FileClass = ::arrow::io::FileOutputStream; |
| std::shared_ptr<FileClass> out_file; |
| PARQUET_THROW_NOT_OK(FileClass::Open(PARQUET_FILENAME, &out_file)); |
| |
| // Setup the parquet schema |
| std::shared_ptr<GroupNode> schema = SetupSchema(); |
| |
| // Add writer properties |
| parquet::WriterProperties::Builder builder; |
| builder.compression(parquet::Compression::SNAPPY); |
| std::shared_ptr<parquet::WriterProperties> props = builder.build(); |
| |
| // Create a ParquetFileWriter instance |
| std::shared_ptr<parquet::ParquetFileWriter> file_writer = |
| parquet::ParquetFileWriter::Open(out_file, schema, props); |
| |
| // Append a RowGroup with a specific number of rows. |
| parquet::RowGroupWriter* rg_writer = file_writer->AppendRowGroup(); |
| |
| // Write the Bool column |
| parquet::BoolWriter* bool_writer = |
| static_cast<parquet::BoolWriter*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| bool value = ((i % 2) == 0) ? true : false; |
| bool_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Write the Int32 column |
| parquet::Int32Writer* int32_writer = |
| static_cast<parquet::Int32Writer*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| int32_t value = i; |
| int32_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Write the Int64 column. Each row has repeats twice. |
| parquet::Int64Writer* int64_writer = |
| static_cast<parquet::Int64Writer*>(rg_writer->NextColumn()); |
| for (int i = 0; i < 2 * NUM_ROWS_PER_ROW_GROUP; i++) { |
| int64_t value = i * 1000 * 1000; |
| value *= 1000 * 1000; |
| int16_t definition_level = 1; |
| int16_t repetition_level = 0; |
| if ((i % 2) == 0) { |
| repetition_level = 1; // start of a new record |
| } |
| int64_writer->WriteBatch(1, &definition_level, &repetition_level, &value); |
| } |
| |
| // Write the INT96 column. |
| parquet::Int96Writer* int96_writer = |
| static_cast<parquet::Int96Writer*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| parquet::Int96 value; |
| value.value[0] = i; |
| value.value[1] = i + 1; |
| value.value[2] = i + 2; |
| int96_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Write the Float column |
| parquet::FloatWriter* float_writer = |
| static_cast<parquet::FloatWriter*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| float value = static_cast<float>(i) * 1.1f; |
| float_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Write the Double column |
| parquet::DoubleWriter* double_writer = |
| static_cast<parquet::DoubleWriter*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| double value = i * 1.1111111; |
| double_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Write the ByteArray column. Make every alternate values NULL |
| parquet::ByteArrayWriter* ba_writer = |
| static_cast<parquet::ByteArrayWriter*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| parquet::ByteArray value; |
| char hello[FIXED_LENGTH] = "parquet"; |
| hello[7] = static_cast<char>(static_cast<int>('0') + i / 100); |
| hello[8] = static_cast<char>(static_cast<int>('0') + (i / 10) % 10); |
| hello[9] = static_cast<char>(static_cast<int>('0') + i % 10); |
| if (i % 2 == 0) { |
| int16_t definition_level = 1; |
| value.ptr = reinterpret_cast<const uint8_t*>(&hello[0]); |
| value.len = FIXED_LENGTH; |
| ba_writer->WriteBatch(1, &definition_level, nullptr, &value); |
| } else { |
| int16_t definition_level = 0; |
| ba_writer->WriteBatch(1, &definition_level, nullptr, nullptr); |
| } |
| } |
| |
| // Write the FixedLengthByteArray column |
| parquet::FixedLenByteArrayWriter* flba_writer = |
| static_cast<parquet::FixedLenByteArrayWriter*>(rg_writer->NextColumn()); |
| for (int i = 0; i < NUM_ROWS_PER_ROW_GROUP; i++) { |
| parquet::FixedLenByteArray value; |
| char v = static_cast<char>(i); |
| char flba[FIXED_LENGTH] = {v, v, v, v, v, v, v, v, v, v}; |
| value.ptr = reinterpret_cast<const uint8_t*>(&flba[0]); |
| |
| flba_writer->WriteBatch(1, nullptr, nullptr, &value); |
| } |
| |
| // Close the ParquetFileWriter |
| file_writer->Close(); |
| |
| // Write the bytes to file |
| DCHECK(out_file->Close().ok()); |
| } catch (const std::exception& e) { |
| std::cerr << "Parquet write error: " << e.what() << std::endl; |
| return -1; |
| } |
| |
| /********************************************************************************** |
| PARQUET READER EXAMPLE |
| **********************************************************************************/ |
| |
| try { |
| // Create a ParquetReader instance |
| std::unique_ptr<parquet::ParquetFileReader> parquet_reader = |
| parquet::ParquetFileReader::OpenFile(PARQUET_FILENAME, false); |
| |
| // Get the File MetaData |
| std::shared_ptr<parquet::FileMetaData> file_metadata = parquet_reader->metadata(); |
| |
| // Get the number of RowGroups |
| int num_row_groups = file_metadata->num_row_groups(); |
| assert(num_row_groups == 1); |
| |
| // Get the number of Columns |
| int num_columns = file_metadata->num_columns(); |
| assert(num_columns == 8); |
| |
| // Iterate over all the RowGroups in the file |
| for (int r = 0; r < num_row_groups; ++r) { |
| // Get the RowGroup Reader |
| std::shared_ptr<parquet::RowGroupReader> row_group_reader = |
| parquet_reader->RowGroup(r); |
| |
| int64_t values_read = 0; |
| int64_t rows_read = 0; |
| int16_t definition_level; |
| int16_t repetition_level; |
| int i; |
| std::shared_ptr<parquet::ColumnReader> column_reader; |
| |
| // Get the Column Reader for the boolean column |
| column_reader = row_group_reader->Column(0); |
| parquet::BoolReader* bool_reader = |
| static_cast<parquet::BoolReader*>(column_reader.get()); |
| |
| // Read all the rows in the column |
| i = 0; |
| while (bool_reader->HasNext()) { |
| bool value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = bool_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| bool expected_value = ((i % 2) == 0) ? true : false; |
| assert(value == expected_value); |
| i++; |
| } |
| |
| // Get the Column Reader for the Int32 column |
| column_reader = row_group_reader->Column(1); |
| parquet::Int32Reader* int32_reader = |
| static_cast<parquet::Int32Reader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (int32_reader->HasNext()) { |
| int32_t value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = int32_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| assert(value == i); |
| i++; |
| } |
| |
| // Get the Column Reader for the Int64 column |
| column_reader = row_group_reader->Column(2); |
| parquet::Int64Reader* int64_reader = |
| static_cast<parquet::Int64Reader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (int64_reader->HasNext()) { |
| int64_t value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = int64_reader->ReadBatch(1, &definition_level, &repetition_level, |
| &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| int64_t expected_value = i * 1000 * 1000; |
| expected_value *= 1000 * 1000; |
| assert(value == expected_value); |
| if ((i % 2) == 0) { |
| assert(repetition_level == 1); |
| } else { |
| assert(repetition_level == 0); |
| } |
| i++; |
| } |
| |
| // Get the Column Reader for the Int96 column |
| column_reader = row_group_reader->Column(3); |
| parquet::Int96Reader* int96_reader = |
| static_cast<parquet::Int96Reader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (int96_reader->HasNext()) { |
| parquet::Int96 value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = int96_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| parquet::Int96 expected_value; |
| expected_value.value[0] = i; |
| expected_value.value[1] = i + 1; |
| expected_value.value[2] = i + 2; |
| for (int j = 0; j < 3; j++) { |
| assert(value.value[j] == expected_value.value[j]); |
| } |
| i++; |
| } |
| |
| // Get the Column Reader for the Float column |
| column_reader = row_group_reader->Column(4); |
| parquet::FloatReader* float_reader = |
| static_cast<parquet::FloatReader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (float_reader->HasNext()) { |
| float value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = float_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| float expected_value = static_cast<float>(i) * 1.1f; |
| assert(value == expected_value); |
| i++; |
| } |
| |
| // Get the Column Reader for the Double column |
| column_reader = row_group_reader->Column(5); |
| parquet::DoubleReader* double_reader = |
| static_cast<parquet::DoubleReader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (double_reader->HasNext()) { |
| double value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = double_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| double expected_value = i * 1.1111111; |
| assert(value == expected_value); |
| i++; |
| } |
| |
| // Get the Column Reader for the ByteArray column |
| column_reader = row_group_reader->Column(6); |
| parquet::ByteArrayReader* ba_reader = |
| static_cast<parquet::ByteArrayReader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (ba_reader->HasNext()) { |
| parquet::ByteArray value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = |
| ba_reader->ReadBatch(1, &definition_level, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // Verify the value written |
| char expected_value[FIXED_LENGTH] = "parquet"; |
| expected_value[7] = static_cast<char>('0' + i / 100); |
| expected_value[8] = static_cast<char>('0' + (i / 10) % 10); |
| expected_value[9] = static_cast<char>('0' + i % 10); |
| if (i % 2 == 0) { // only alternate values exist |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| assert(value.len == FIXED_LENGTH); |
| assert(memcmp(value.ptr, &expected_value[0], FIXED_LENGTH) == 0); |
| assert(definition_level == 1); |
| } else { |
| // There are NULL values in the rows written |
| assert(values_read == 0); |
| assert(definition_level == 0); |
| } |
| i++; |
| } |
| |
| // Get the Column Reader for the FixedLengthByteArray column |
| column_reader = row_group_reader->Column(7); |
| parquet::FixedLenByteArrayReader* flba_reader = |
| static_cast<parquet::FixedLenByteArrayReader*>(column_reader.get()); |
| // Read all the rows in the column |
| i = 0; |
| while (flba_reader->HasNext()) { |
| parquet::FixedLenByteArray value; |
| // Read one value at a time. The number of rows read is returned. values_read |
| // contains the number of non-null rows |
| rows_read = flba_reader->ReadBatch(1, nullptr, nullptr, &value, &values_read); |
| // Ensure only one value is read |
| assert(rows_read == 1); |
| // There are no NULL values in the rows written |
| assert(values_read == 1); |
| // Verify the value written |
| char v = static_cast<char>(i); |
| char expected_value[FIXED_LENGTH] = {v, v, v, v, v, v, v, v, v, v}; |
| assert(memcmp(value.ptr, &expected_value[0], FIXED_LENGTH) == 0); |
| i++; |
| } |
| } |
| } catch (const std::exception& e) { |
| std::cerr << "Parquet read error: " << e.what() << std::endl; |
| return -1; |
| } |
| |
| std::cout << "Parquet Writing and Reading Complete" << std::endl; |
| |
| return 0; |
| } |