For connector c++ 1.1, in this example, it's quite easy to get values by specifying the column name (or alias name).
But when I upgraded to version 8.0 xdevapi, I found this feature is no longer supported.
#include <mysqlx/xdevapi.h>
using namespace std;
using namespace mysqlx;
Session sess(<server_url>);
auto result = sess.sql("SELECT * FROM student").execute();
Row row = result.fetchOne();
cout << row[0] << endl; // <- ok
cout << row["ID"] << endl; // <- can compile but garbage output
cout << row.get("ID") << endl; // <- cannot compile
I know the column names can be retrieved from result.getColumn(n).getColumnLabel()
, but IMO it's useless. A "field" -> "index" mapping can really help the developers.
I'm new to C++, so the following sentenses maybe too naive. Here's the possible ways I guess:
result.getColumns()
, then check the getColumnLabel()
indexOf
? But I find result.getColumns()
does not support this method since it's a deque
There is no way, at the moment, to get the column value using name.
A way is, as you suggest, a map with the name / index pair.
Something like this would work:
SqlResult sql_res = sess.sql("select * from table").execute();
std::map<std::string, size_t> columns;
auto fill_columns = [&sql_res, &columns]() -> void
{
size_t idx = 0;
for (auto &el : sql_res.getColumns())
{
columns.emplace(std::make_pair(el.getColumnLabel(), idx++));
}
};
fill_columns();
And then, using it:
for(auto row : sql_res)
{
std::cout << "a:" << row[columns["a"]] << std::endl;
std::cout << "b:" << row[columns["b"]] << std::endl;
}