/// <summary>
/// Asynchronously but eagerly fetches a set of rows, up to the specified count, providing a page of results with a next page token
/// if more results are available. This is typically used within web applications, where the next page token
/// is propagated to the client along with the results, so that the next page can be retrieved in another request.
/// </summary>
/// <param name="pageSize">The maximum number of rows to retrieve. Must be positive.</param>
/// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
/// <returns>A task representing the asynchronous operation. When complete, the result is
/// an in-memory result set of at most the given number of rows.</returns>
public async Task <BigQueryPage> ReadPageAsync(int pageSize, CancellationToken cancellationToken = default)
{
GaxPreconditions.CheckArgumentRange(pageSize, nameof(pageSize), 1, int.MaxValue);
GetQueryResultsOptions clonedOptions = _options?.Clone() ?? new GetQueryResultsOptions();
List <BigQueryRow> rows = new List <BigQueryRow>(pageSize);
// Work out whether to use the response we've already got, or create a new one.
GetQueryResultsResponse response = _response;
if (response.Rows?.Count > pageSize)
{
// Oops. Do it again from scratch, with a useful page size.
clonedOptions.PageSize = pageSize;
response = await _client.GetRawQueryResultsAsync(JobReference, clonedOptions, timeoutBase : null, cancellationToken).ConfigureAwait(false);
}
// First add the rows from the existing response.
rows.AddRange(ConvertResponseRows(response));
string pageToken = response.PageToken;
clonedOptions.StartIndex = null;
// Now keep going until we've filled the result set or know there's no more data.
while (rows.Count < pageSize && pageToken != null)
{
clonedOptions.PageToken = pageToken;
clonedOptions.PageSize = pageSize - rows.Count;
var nextResponse = await _client.GetRawQueryResultsAsync(JobReference, clonedOptions, timeoutBase : null, cancellationToken).ConfigureAwait(false);
rows.AddRange(ConvertResponseRows(nextResponse));
pageToken = nextResponse.PageToken;
}
return(new BigQueryPage(rows, Schema, JobReference, TableReference, pageToken));
}
