how to dump query results into nt format in virtuoso

This is on ubuntu 14.04 LTS

1. you need to install virtuoso (you can refer to my previous post)

2. open your virtuoso service

3. do

./isql 1111

to invoke the virtuosl‘s isql interface

4. copy and past the following: (source: click me )

/**
 * Dumps the result of the given select-sparql query into a file
 * or a sequence of files based on a file size limit.
 *
 * @param query A select query. Only the first three variables in the projection will be dumped
 * @param out_file A base filename. ‘.nt‘ will be autmatically appended.
 * @param file_length_limit A result set is split to multiple files according to this limit.
 *        If it is greater 0 a sequence number will be appended to the filename.
 */
drop procedure dump_query_nt;
create procedure dump_query_nt(in query varchar, in out_file varchar, in file_length_limit integer := -1)
{
    declare file_name varchar;
    declare env, ses any;
    declare ses_len, max_ses_len, file_len, file_idx integer;
    declare state, msg, descs any;
    declare chandle any;
    declare sub any;
    declare sql any;
    set isolation = ‘uncommitted‘;
    max_ses_len := 10000000;
    file_len := 0;
    file_idx := 1;

    if(file_length_limit >= 0) {
        file_name := sprintf (‘%s-%06d.nt‘, out_file, file_idx);
    } else {
        file_name := sprintf (‘%s.nt‘, out_file);
    }

    string_to_file (file_name || ‘.query‘, query, -2);
    env := vector (0, 0, 0);
    ses := string_output ();

    state := ‘00000‘;
    sql := sprintf(‘sparql define input:storage "" %s‘, query);

    exec(sql, state, msg, vector (), 0, descs, null, chandle);
    if (state <> ‘00000‘) {
        signal (state, msg);
    }

    while(exec_next(chandle, state, msg, sub) = 0) {
        if (state <> ‘00000‘) {
            signal (state, msg);
        }

        http_nt_triple (env, sub[0], sub[1], sub[2], ses);
        ses_len := length (ses);

        if (ses_len > max_ses_len) {
            file_len := file_len + ses_len;
            if (file_length_limit >= 0 and file_len > file_length_limit) {
                string_to_file (file_name, ses, -1);
                file_len := 0;
                file_idx := file_idx + 1;
                file_name := sprintf (‘%s-%06d.nt‘, out_file, file_idx);
                env := vector (0, 0, 0);
            }
            else {
              string_to_file (file_name, ses, -1);
            }

            ses := string_output ();
        }
    }
    if (length (ses)) {
        string_to_file (file_name, ses, -1);
    }

    exec_close(chandle);
};

5. hit enter to regester this dump_query_nt function

6. an example of usage of this function is as follows:

dump_query_nt(‘Select ?s ?p ?o { ?s a ?c . ?s ?p ?o . }‘, ‘/tmp/result‘);

you input this in the prompt, make sure /temp/result directory is accessible for virtuoso. you could go to virtuoso.ini (under certain directory) to config it.