/// <inheritdoc />
public override Task<bool> ReadAsync(CancellationToken cancellationToken)
{
return ExecuteHelper.WithErrorTranslationAndProfiling(
async () =>
{
await PopulateMetadataAsync(cancellationToken).ConfigureAwait(false);
_innerList.Clear();
//read # values == # fields.
var first = await _resultSet.NextAsync(cancellationToken).ConfigureAwait(false);
if (first == null)
{
return false;
}
_innerList.Add(first);
//we expect to get full rows...
for (var i = 1; i < _metadata.RowType.Fields.Count; i++)
{
_innerList.Add(await _resultSet.NextAsync(cancellationToken).ConfigureAwait(false));
}
return true;
},
"SpannerDataReader.Read");
}
/// <summary>
/// Reads the next row of values from Cloud Spanner.
/// Important: Cloud Spanner supports limited cancellation of this task.
/// </summary>
/// <param name="cancellationToken">A cancellation token to cancel the read. Cloud Spanner currently
/// supports limited cancellation while advancing the read to the next row.</param>
/// <returns>True if another row was read.</returns>
public override Task <bool> ReadAsync(CancellationToken cancellationToken)
{
return(ExecuteHelper.WithErrorTranslationAndProfiling(
async() =>
{
if (_metadata == null)
{
await PopulateMetadataAsync(cancellationToken).ConfigureAwait(false);
}
_rowValid = false;
_innerList.Clear();
var first = await _resultSet.NextAsync(cancellationToken).ConfigureAwait(false);
if (first == null)
{
return false;
}
_innerList.Add(first);
// We expect to get full rows...
for (var i = 1; i < _metadata.RowType.Fields.Count; i++)
{
var value = await _resultSet.NextAsync(cancellationToken).ConfigureAwait(false);
GaxPreconditions.CheckState(value != null, "Incomplete row returned by Spanner server");
_innerList.Add(value);
}
_rowValid = true;
return true;
},
"SpannerDataReader.Read", Logger));
}
/// <summary>
/// Reads the next row of values from Cloud Spanner.
/// Important: Cloud Spanner supports limited cancellation of this task.
/// </summary>
/// <param name="cancellationToken">A cancellation token to cancel the read. Cloud Spanner currently
/// supports limited cancellation while advancing the read to the next row.</param>
/// <returns>True if another row was read.</returns>
public override Task <bool> ReadAsync(CancellationToken cancellationToken) =>
ExecuteHelper.WithErrorTranslationAndProfiling(async() =>
{
using (var timeoutCts = new CancellationTokenSource(TimeSpan.FromSeconds(_readTimeoutSeconds)))
{
var timeoutToken = timeoutCts.Token;
using (var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutToken))
{
try
{
var effectiveToken = linkedCts.Token;
if (_metadata == null)
{
await PopulateMetadataAsync(effectiveToken).ConfigureAwait(false);
}
_rowValid = false;
_innerList.Clear();
var first = await _resultSet.NextAsync(effectiveToken).ConfigureAwait(false);
if (first == null)
{
// If this is the first thing we've tried to read, then we know there are no rows.
if (_hasRows == null)
{
_hasRows = false;
}
return(false);
}
_innerList.Add(first);
// We expect to get full rows...
for (var i = 1; i < _metadata.RowType.Fields.Count; i++)
{
var value = await _resultSet.NextAsync(effectiveToken).ConfigureAwait(false);
GaxPreconditions.CheckState(value != null, "Incomplete row returned by Spanner server");
_innerList.Add(value);
}
_rowValid = true;
_hasRows = true;
return(true);
}
// Translate timeouts from our own cancellation token into a Spanner exception.
// This mimics the behavior of SqlDataReader, which throws a SqlException on timeout.
// It's *possible* that the operation was cancelled due to the user-provided cancellation token,
// and that it just happens that the timeout has been fired as well... but there's a race
// condition anyway in that case, so it's probably reasonable to take the simple path.
catch (OperationCanceledException) when(timeoutToken.IsCancellationRequested)
{
throw new SpannerException(ErrorCode.DeadlineExceeded, "Read operation timed out");
}
}
}
},
"SpannerDataReader.Read", Logger);