/// <summary>
/// Reads from the reader until there are no more results to read
/// </summary>
/// <param name="cancellationToken">Cancellation token for cancelling the query</param>
public async Task ReadResultToEnd(CancellationToken cancellationToken)
{
// Mark that result has been read
hasBeenRead = true;
// Open a writer for the file
using (IFileStreamWriter fileWriter = fileStreamFactory.GetWriter(outputFileName, MaxCharsToStore, MaxXmlCharsToStore))
{
// If we can initialize the columns using the column schema, use that
if (!DataReader.DbDataReader.CanGetColumnSchema())
{
throw new InvalidOperationException(SR.QueryServiceResultSetNoColumnSchema);
}
Columns = DataReader.Columns;
long currentFileOffset = 0;
while (await DataReader.ReadAsync(cancellationToken))
{
RowCount++;
FileOffsets.Add(currentFileOffset);
currentFileOffset += fileWriter.WriteRow(DataReader);
}
}
// Check if resultset is 'for xml/json'. If it is, set isJson/isXml value in column metadata
SingleColumnXmlJsonResultSet();
}
/// <summary>
/// Generates a subset of the rows from the result set
/// </summary>
/// <param name="startRow">The starting row of the results</param>
/// <param name="rowCount">How many rows to retrieve</param>
/// <returns>A subset of results</returns>
public Task <ResultSetSubset> GetSubset(int startRow, int rowCount)
{
// Sanity check to make sure that the results have been read beforehand
if (!hasBeenRead)
{
throw new InvalidOperationException(SR.QueryServiceResultSetNotRead);
}
// Sanity check to make sure that the row and the row count are within bounds
if (startRow < 0 || startRow >= RowCount)
{
throw new ArgumentOutOfRangeException(nameof(startRow), SR.QueryServiceResultSetStartRowOutOfRange);
}
if (rowCount <= 0)
{
throw new ArgumentOutOfRangeException(nameof(rowCount), SR.QueryServiceResultSetRowCountOutOfRange);
}
return(Task.Factory.StartNew(() =>
{
string[][] rows;
using (IFileStreamReader fileStreamReader = fileStreamFactory.GetReader(outputFileName))
{
// If result set is 'for xml' or 'for json',
// Concatenate all the rows together into one row
if (isSingleColumnXmlJsonResultSet)
{
// Iterate over all the rows and process them into a list of string builders
IEnumerable <string> rowValues = FileOffsets.Select(rowOffset => fileStreamReader.ReadRow(rowOffset, Columns)[0].DisplayValue);
rows = new[] { new[] { string.Join(string.Empty, rowValues) } };
}
else
{
// Figure out which rows we need to read back
IEnumerable <long> rowOffsets = FileOffsets.Skip(startRow).Take(rowCount);
// Iterate over the rows we need and process them into output
rows = rowOffsets.Select(rowOffset =>
fileStreamReader.ReadRow(rowOffset, Columns).Select(cell => cell.DisplayValue).ToArray())
.ToArray();
}
}
// Retrieve the subset of the results as per the request
return new ResultSetSubset
{
Rows = rows,
RowCount = rows.Length
};
}));
}
