Using pqxx cursors - postgresql

Question

I am trying to learn how to use cursors in pqxx.
I found pqxx::cursor_base in the reference and there are several subclasses that derive from pqxx::cursor_base.
After Googling the topic for hours, I can't find any sample code or anything explaining how to use pqxx cursors.
Any suggestions?

Answer 1

There are surprisingly few cursor examples to be found. Here's what I use:
const std::conStr("user=" + opt::dbUser + " password=" + opt::dbPasswd + " host=" + opt::dbHost + " dbname=" + opt::dbName);
pqxx::connection conn(connStr);
pqxx::work txn(conn);
std::string selectString = "SELECT id, name FROM table_name WHERE condition";
pqxx::stateless_cursor<pqxx::cursor_base::read_only, pqxx::cursor_base::owned>
cursor(txn, selectString, "myCursor", false);
//cursor variables
size_t idx = 0; //starting location
size_t step = 10000; //number of rows for each chunk
pqxx::result result;
do{
//get next cursor chunk and update the index
result = cursor.retrieve( idx, idx + step );
idx += step;
size_t records = result.size();
cout << idx << ": records pulled = " << records << endl;
for( pqxx::result::const_iterator row : result ){
//iterate over cursor rows
}
}
while( result.size() == step ); //if the result.size() != step, we're on our last loop
cout << "Done!" << endl;