Aggreagation hash function in arrow cpp

[Prrix]

I am not able to work with the hash function impelmentation , tryna figure out how to groupby and get last values and its indx or something but its not working with syntax errors , can someone help !

[drin]

what have you been trying?

[zanmato1984]

Hi @Prrix , it would be helpful if you paste your C++ code and the error message here.

Meanwhile you can refer to the aggregation example code in the source tree:

arrow/cpp/examples/arrow/execution_plan_documentation_examples.cc

Lines 456 to 480 in bf5df5b

	/// \brief An example showing an aggregation node to perform a group-by operation
	///
	/// Source-Aggregation-Table
	/// This example shows how an aggregation operation can be applied on a
	/// execution plan resulting in grouped output. The source node loads the
	/// data and the aggregation (counting unique types in column 'a') is
	/// applied on this data. The output is collected into a table that will contain
	/// one row for each unique combination of group keys.
	arrow::Status SourceGroupAggregateSinkExample() {
	ARROW_ASSIGN_OR_RAISE(auto basic_data, MakeBasicBatches());
	arrow::AsyncGenerator<std::optional<cp::ExecBatch>> sink_gen;
	auto source_node_options = ac::SourceNodeOptions{basic_data.schema, basic_data.gen()};
	ac::Declaration source{"source", std::move(source_node_options)};
	auto options = std::make_shared<cp::CountOptions>(cp::CountOptions::ONLY_VALID);
	auto aggregate_options =
	ac::AggregateNodeOptions{/*aggregates=*/{{"hash_count", options, "a", "count(a)"}},
	/*keys=*/{"b"}};
	ac::Declaration aggregate{
	"aggregate", {std::move(source)}, std::move(aggregate_options)};
	return ExecutePlanAndCollectAsTable(std::move(aggregate));
	}