libpqxx steam_to example

#include <iostream>
#include <string>
#include <pqxx/pqxx>

std::basic_string<std::byte> randomizer(int size)
{
	std::basic_string<std::byte> n;
	for(int j = 0; j < size; ++j)
	{
		std::byte b;
		b = (std::byte)(std::rand() % 255);
		n.push_back(b);
	};

	return n;
}

int main()
{
	const std::string connstr = "user=postgres dbname=octopus password=postgres";

	try
	{
		{
			pqxx::connection c(connstr);
			pqxx::work w(c);
			w.exec("DROP TABLE iF EXISTS test_streamto");
			w.exec("CREATE TABLE test_streamto ( "
			       "idx serial primary KEY, "
			       "strx character varying(5) not NULL, "
			       "datax BYTEA"

			       ");");

			w.commit();
			std::cout << "recreated table" << std::endl;
		}

		//10K rows with 10K bytes gives a table size of 119 megabytes in ~20 seconds on a 2.4GHz I7 9th gen in debug mode (4 seconds in release mode)

		const int LOOPCOUNT = 10000;
		{
			pqxx::connection c(connstr);
			pqxx::work w(c);

			pqxx::stream_to stream_to{ w
			                           , "test_streamto"
			                           , std::vector<std::string>{"strx", "datax"} };

			for(int j = 0; j < LOOPCOUNT; ++j)
			{
				std::string text = "t" + std::to_string(j);
				std::tuple<std::string, std::basic_string<std::byte>> data(text, randomizer(10000));

				stream_to << data;
			}
			stream_to.complete();
			w.commit();
		}

		{
			pqxx::connection c(connstr);
			pqxx::work w(c);
			pqxx::result r = w.exec("SELECT COUNT (idx)  AS cnt FROM test_streamto");
			w.commit();

			int cnt = r[0]["cnt"].as<int>();
			if(LOOPCOUNT != cnt)
			{
				throw "damn stream_to thingomobob";
			}
		}
	}
	catch(const std::exception& e)
	{
		std::cout << e.what();
		return -1;
	}

	return 0;
}