cyb70289 commented on a change in pull request #11231: URL: https://github.com/apache/arrow/pull/11231#discussion_r716124933
########## File path: cpp/examples/arrow/compute_and_write_csv_example.cc ########## @@ -0,0 +1,130 @@ +// 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/compute/api_aggregate.h> +#include <arrow/compute/cast.h> +#include <arrow/compute/exec/expression.h> +#include <arrow/csv/api.h> +#include <arrow/csv/writer.h> +#include <arrow/io/file.h> +#include <arrow/io/interfaces.h> +#include <arrow/result.h> +#include <arrow/status.h> +#include <iostream> +#include <vector> + +// Many operations in Apache arrow operate on +// columns of data, and the columns of data are +// assembled into a table. In this example, we +// examine how to compare two arrays which are +// combined to form a table that is then written +// out to a CSV file. + +#define ABORT_ON_FAILURE(expr) \ + do { \ + arrow::Status status_ = (expr); \ + if (!status_.ok()) { \ + std::cerr << status_.message() << std::endl; \ + abort(); \ + } \ + } while (0); + + +int main(int argc, char** argv){ + const char* csv_filename = "output.csv"; + + // Make Arrays + arrow::NumericBuilder<arrow::Int64Type> int64_builder; + arrow::BooleanBuilder boolean_builder; + + // Make place for 8 values in total + ABORT_ON_FAILURE(int64_builder.Resize(8)); + ABORT_ON_FAILURE(boolean_builder.Resize(8)); + + // Bulk append the given values + std::vector<int64_t> int64_values = {1, 2, 3, 4, 5, 6, 7, 8}; + ABORT_ON_FAILURE(int64_builder.AppendValues(int64_values)); + std::shared_ptr<arrow::Array> array_a; + ABORT_ON_FAILURE(int64_builder.Finish(&array_a)); + int64_builder.Reset(); + int64_values = {2, 5, 1, 3, 6, 2, 7, 4}; + std::shared_ptr<arrow::Array> array_b; + ABORT_ON_FAILURE(int64_builder.AppendValues(int64_values)); + ABORT_ON_FAILURE(int64_builder.Finish(&array_b)); + + // Cast the Arrays to their actual types + auto int64_array_a = std::static_pointer_cast<arrow::Int64Array>(array_a); + auto int64_array_b = std::static_pointer_cast<arrow::Int64Array>(array_b); + for(int64_t i=0; i < 8; i++) + { + if( (!int64_array_a->IsNull(i)) & + (!int64_array_b->IsNull(i)) ) + { + bool comparison_result = int64_array_a->Value(i) > + int64_array_b->Value(i); + boolean_builder.UnsafeAppend(comparison_result); + } + } + std::shared_ptr<arrow::Array> array_c; + ABORT_ON_FAILURE(boolean_builder.Finish(&array_c)); + //auto bool_array_c = std::static_pointer_cast<arrow::BooleanArray>(array_c); + std::cout << "Array created" << std::endl; + + // Try a compute function + arrow::Datum compared_datum; + std::shared_ptr<arrow::Array> compared_array; + //auto bool_compared_array = std::static_pointer_cast<arrow::BooleanArray>(compared_array); + arrow::Result<arrow::Datum> st_compared_datum = + arrow::compute::CallFunction("greater",{array_a,array_b}); + if (st_compared_datum.ok()) { + compared_datum = std::move(st_compared_datum).ValueOrDie(); + compared_array = compared_datum.make_array(); + }else{ + std::cerr << st_compared_datum.status() << std::endl; + } + // Create a table + auto schema = arrow::schema({arrow::field("a", arrow::int64()), + arrow::field("b", arrow::int64()), + arrow::field("c", arrow::boolean()), + arrow::field("d", arrow::boolean()) }); + std::shared_ptr<arrow::Table> my_table = arrow::Table::Make(schema, {array_a,array_b,array_c, + compared_array}); + + std::cout << "Table created" << std::endl; + + // Write table to CSV file Review comment: Though it's an example, I think we should still be careful not to accidentally destroy a possible same named file under current directory. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
