private async Task <Slice> GetPreviousNodeAsync(IFdbTransaction trans, int level, Slice key)
{
// GetPreviousNodeAsync looks for the previous node on a level, but "doesn't care"
// about the contents of that node. It therefore uses a non-isolated (snaphot)
// read and explicitly adds a conflict range that is exclusive of the actual,
// found previous node. This allows an increment of that node not to trigger
// a transaction conflict. We also add a conflict key on the found previous
// key in level 0. This allows detection of erasures.
var k = this.Subspace.Encode(level, key);
//Console.WriteLine(k);
//Console.WriteLine("GetPreviousNode(" + level + ", " + key + ")");
//Console.WriteLine(KeySelector.LastLessThan(k) + " <= x < " + KeySelector.FirstGreaterOrEqual(k));
var kv = await trans
.Snapshot
.GetRange(
KeySelector.LastLessThan(k),
KeySelector.FirstGreaterOrEqual(k)
)
.FirstAsync()
.ConfigureAwait(false);
//Console.WriteLine("Found " + FdbKey.Dump(kv.Key));
var prevKey = this.Subspace.DecodeLast <Slice>(kv.Key);
trans.AddReadConflictRange(kv.Key + FdbKey.MinValue, k);
trans.AddReadConflictKey(this.Subspace.Encode(0, prevKey));
return(prevKey);
}
private async Task<Slice> GetPreviousNodeAsync(IFdbTransaction trans, int level, Slice key)
{
// GetPreviousNodeAsync looks for the previous node on a level, but "doesn't care"
// about the contents of that node. It therefore uses a non-isolated (snaphot)
// read and explicitly adds a conflict range that is exclusive of the actual,
// found previous node. This allows an increment of that node not to trigger
// a transaction conflict. We also add a conflict key on the found previous
// key in level 0. This allows detection of erasures.
var k = this.Subspace.Pack(level, key);
//Console.WriteLine(k);
//Console.WriteLine("GetPreviousNode(" + level + ", " + key + ")");
//Console.WriteLine(FdbKeySelector.LastLessThan(k) + " <= x < " + FdbKeySelector.FirstGreaterOrEqual(k));
var kv = await trans
.Snapshot
.GetRange(
FdbKeySelector.LastLessThan(k),
FdbKeySelector.FirstGreaterOrEqual(k)
)
.FirstAsync()
.ConfigureAwait(false);
//Console.WriteLine("Found " + FdbKey.Dump(kv.Key));
var prevKey = this.Subspace.UnpackLast<Slice>(kv.Key);
trans.AddReadConflictRange(kv.Key + FdbKey.MinValue, k);
trans.AddReadConflictKey(this.Subspace.Pack(0, prevKey));
return prevKey;
}