private static async Task <List <Slice> > GetBoundaryKeysInternalAsync([NotNull] IFdbReadOnlyTransaction trans, Slice begin, Slice end)
{
Contract.Requires(trans != null && end >= begin);
#if TRACE_COUNTING
trans.Annotate("Get boundary keys in range {0}", KeyRange.Create(begin, end));
#endif
trans.WithReadAccessToSystemKeys();
var results = new List <Slice>();
int iterations = 0;
var options = new FdbRangeOptions {
Mode = FdbStreamingMode.WantAll
};
while (begin < end)
{
FdbException error = null;
Slice lastBegin = begin;
try
{
var chunk = await trans.Snapshot.GetRangeAsync(KeyServers + begin, KeyServers + end, options, iterations).ConfigureAwait(false);
++iterations;
if (chunk.Count > 0)
{
foreach (var kvp in chunk)
{
results.Add(kvp.Key.Substring(KeyServers.Count));
}
begin = chunk.Last.Substring(KeyServers.Count) + 0;
}
if (!chunk.HasMore)
{
begin = end;
}
}
catch (FdbException e)
{
error = e;
}
if (error != null)
{
if (error.Code == FdbError.PastVersion && begin != lastBegin)
{ // if we get a PastVersion and *something* has happened, then we are no longer transactional
trans.Reset();
}
else
{
await trans.OnErrorAsync(error.Code).ConfigureAwait(false);
}
iterations = 0;
trans.WithReadAccessToSystemKeys();
}
}
#if TRACE_COUNTING
if (results.Count == 0)
{
trans.Annotate("There is no chunk boundary in range {0}", KeyRange.Create(begin, end));
}
else
{
trans.Annotate("Found {0} boundaries in {1} iteration(s)", results.Count, iterations);
}
#endif
return(results);
}