As these questions point out, Guid.NewGuid will return the same value for all rows due to the enforced deterministic nature of U-SQL i.e if it's scaled out if an element (vertex) needs retrying then it should return the same value....
Guid.NewGuid() always return same Guid for all rows
auto_increment in U-SQL
However.... the code example in the officials documentation for a User Defined Extractor purposefully uses Guid.NewGuid().
I'm not querying the validity of the answers for the questions above, as they are from an authoritative source (the programme manager for u-sql, so very authoritative!). However, what I'm wondering if the action of using an Extractor means NewGuid can be used as normal? Is it simply within c# expressions in u-sql and User Defined Functions in which NewGuid is unsafe?
[SqlUserDefinedExtractor(AtomicFileProcessing = true)]
public class FullDescriptionExtractor : IExtractor
{
private Encoding _encoding;
private byte[] _row_delim;
private char _col_delim;
public FullDescriptionExtractor(Encoding encoding, string row_delim = "\r\n", char col_delim = '\t')
{
this._encoding = ((encoding == null) ? Encoding.UTF8 : encoding);
this._row_delim = this._encoding.GetBytes(row_delim);
this._col_delim = col_delim;
}
public override IEnumerable<IRow> Extract(IUnstructuredReader input, IUpdatableRow output)
{
string line;
//Read the input line by line
foreach (Stream current in input.Split(_encoding.GetBytes("\r\n")))
{
using (System.IO.StreamReader streamReader = new StreamReader(current, this._encoding))
{
line = streamReader.ReadToEnd().Trim();
//Split the input by the column delimiter
string[] parts = line.Split(this._col_delim);
int count = 0; // start with first column
foreach (string part in parts)
{
if (count == 0)
{ // for column “guid”, re-generated guid
Guid new_guid = Guid.NewGuid();
output.Set<Guid>(count, new_guid);
}
else if (count == 2)
{
// for column “user”, convert to UPPER case
output.Set<string>(count, part.ToUpper());
}
else
{
// keep the rest of the columns as-is
output.Set<string>(count, part);
}
count += 1;
}
}
yield return output.AsReadOnly();
}
yield break;
}
}
https://docs.microsoft.com/en-us/azure/data-lake-analytics/data-lake-analytics-u-sql-programmability-guide#use-user-defined-extractors
