public Block(StorageOptions storageOptions, ReadOptions readOptions, BlockHandle handle, FileData fileData)
{
try
{
_handle = handle;
_storageOptions = storageOptions;
_fileData = fileData;
if (handle.Position > fileData.Size || (handle.Position + handle.Count + BlockTrailerSize) > fileData.Size)
throw new CorruptedDataException("The specified accessor is beyond the bounds of the provided mappedFile");
_accessor = _fileData.File.CreateAccessor(handle.Position, handle.Count + BlockTrailerSize);
if (readOptions.VerifyChecksums)
{
var crc = Crc.Unmask(_accessor.ReadInt32(handle.Count + 1));
var actualCrc = CalculateActualCrc(handle.Count + 1); // data + tag
if (crc != actualCrc)
throw new CorruptedDataException("block checksum mismatch");
}
RestartsCount = _accessor.ReadInt32(handle.Count - sizeof(int));
RestartsOffset = handle.Count - (RestartsCount * sizeof(int)) - sizeof(int);
if (RestartsOffset > handle.Count)
throw new CorruptedDataException("restart offset wrapped around");
}
catch (Exception)
{
Dispose();
throw;
}
}
public DbIterator NewIterator(ReadOptions options)
{
var result = state.NewInternalIterator(options);
var internalIterator = result.Item1;
var latestSnapshot = result.Item2;
return new DbIterator(state, internalIterator, options.Snapshot != null ? options.Snapshot.Sequence : latestSnapshot);
}
public TwoLevelIterator(
IIterator indexIterator,
Func<ReadOptions, BlockHandle, IIterator> getIterator,
ReadOptions readOptions
)
{
_indexIterator = indexIterator;
_readOptions = readOptions;
this.getIterator = getIterator;
}
public Stream Read(Slice key, ReadOptions options = null)
{
if (options == null)
{
options = new ReadOptions();
}
var mem = state.MemTable;
var imm = state.ImmutableMemTable;
var currentVersion = state.VersionSet.Current;
var snapshot = options.Snapshot != null ? options.Snapshot.Sequence : state.VersionSet.LastSequence;
var reference = new Reference<Slice> { Value = key };
state.PerfCounters.Read();
Stream stream;
GetStats stats;
if (mem.TryGet(reference.Value, snapshot, out stream))
{
state.PerfCounters.BytesRead(stream.Length);
return stream;
}
if (imm != null && imm.TryGet(reference.Value, snapshot, out stream))
{
state.PerfCounters.BytesRead(stream.Length);
return stream;
}
if (currentVersion.TryGet(reference.Value, snapshot, options, out stream, out stats))
{
if (currentVersion.UpdateStats(stats))
{
Background.Work(MaybeScheduleCompactionAsync());
}
state.PerfCounters.BytesRead(stream.Length);
return stream;
}
return null;
}
public IIterator NewIterator(ReadOptions options, ulong fileNumber, long fileSize)
{
try
{
var table = FindTable(fileNumber, fileSize);
return table.CreateIterator(options);
}
catch (Exception e)
{
log.InfoException("Could not open iterator for " + fileNumber + ", will return empty iterator", e);
if (state.Options.ParanoidChecks)
throw;
return new EmptyIterator();
}
}
internal IIterator GetFileIterator(ReadOptions readOptions, BlockHandle handle)
{
var fileNumber = (ulong)handle.Position;
var fileSize = handle.Count;
return storageContext.TableCache.NewIterator(readOptions, fileNumber, fileSize);
}
public IIterator MakeInputIterator(Compaction compaction)
{
var readOptions = new ReadOptions
{
VerifyChecksums = storageContext.Options.ParanoidChecks,
FillCache = false
};
// Level-0 files have to be merged together. For other levels,
// we will make a concatenating iterator per level.
// TODO(opt): use concatenating iterator for level-0 if there is no overlap
var list = new List<IIterator>();
for (int which = 0; which < 2; which++)
{
if (compaction.Inputs[which].Count != 0)
{
if (compaction.Level + which == 0)
{
var files = new List<FileMetadata>(compaction.Inputs[which]);
list.AddRange(files.Select(file => storageContext.TableCache.NewIterator(readOptions, file.FileNumber, file.FileSize)));
}
else
{
// Create concatenating iterator for the files from this level
list.Add(new TwoLevelIterator(
new LevelFileNumIterator(storageContext.InternalKeyComparator, compaction.Inputs[which]),
GetFileIterator, readOptions));
}
}
}
return NewMergingIterator(storageContext.InternalKeyComparator, list);
}
public ItemState Get(InternalKey key, ulong fileNumber, long fileSize, ReadOptions readOptions, IComparator comparator,
out Stream stream)
{
Table table = FindTable(fileNumber, fileSize);
Tuple<Slice, Stream> result = table.InternalGet(readOptions, key);
stream = null;
if (result == null)
{
return ItemState.NotFound;
}
bool shouldDispose = true;
try
{
InternalKey internalKey;
if (!InternalKey.TryParse(result.Item1, out internalKey))
{
return ItemState.Corrupt;
}
if (comparator.Compare(internalKey.UserKey, key.UserKey) == 0)
{
bool isFound = internalKey.Type == ItemType.Value;
if (!isFound)
{
return ItemState.Deleted;
}
stream = result.Item2;
shouldDispose = false;
return ItemState.Found;
}
return ItemState.NotFound;
}
finally
{
if (shouldDispose && result.Item2 != null)
result.Item2.Dispose();
}
}
public bool TryGet(Slice key, ulong seq, ReadOptions readOptions, out Stream stream, out GetStats stats)
{
stats = new GetStats
{
SeekFile = null,
SeekFileLevel = -1
};
FileMetadata lastFileRead = null;
int lastFileReadLevel = -1;
var internalKey = new InternalKey(key, seq, ItemType.ValueForSeek);
// We can search level-by-level since entries never hop across
// levels. Therefore we are guaranteed that if we find data
// in an smaller level, later levels are irrelevant.
for (var level = 0; level < Config.NumberOfLevels; level++)
{
if (Files[level].Count == 0)
{
continue;
}
// Get the list of files to search in this level
var files = GetRelevantFilesForLevel(level, internalKey);
if (files == null || files.Count == 0)
continue;
foreach (var f in files)
{
if (lastFileRead != null && stats.SeekFile == null)
{
// We have had more than one seek for this read. Charge the 1st file.
stats.SeekFile = lastFileRead;
stats.SeekFileLevel = lastFileReadLevel;
}
lastFileRead = f;
lastFileReadLevel = level;
var state = storageContext.TableCache.Get(
internalKey,
f.FileNumber,
f.FileSize,
readOptions,
storageContext.InternalKeyComparator.UserComparator,
out stream);
switch (state)
{
case ItemState.Found:
return true;
case ItemState.NotFound:
break;
case ItemState.Deleted:
return false;
case ItemState.Corrupt:
return false;
default:
throw new NotSupportedException(state.ToString());
}
}
}
stream = null;
return false;
}
private IIterator CreateFileIterator(FileMetadata file)
{
var readOptions = new ReadOptions
{
VerifyChecksums = state.Options.ParanoidChecks,
FillCache = false
};
return state.TableCache.NewIterator(readOptions, file.FileNumber, file.FileSize);
}
private IIterator CreateInputIterator(CompactionState compactionState)
{
var readOptions = new ReadOptions
{
VerifyChecksums = state.Options.ParanoidChecks,
FillCache = false
};
return new MergingIterator(state.InternalKeyComparator, compactionState.Compaction.Inputs[0].Select(x => state.TableCache.NewIterator(readOptions, x.FileNumber, x.FileSize)).ToList());
}
public Tuple<IIterator, ulong> NewInternalIterator(ReadOptions options)
{
var mem = MemTable;
var imm = ImmutableMemTable;
var currentVersion = VersionSet.Current;
var snapshot = options.Snapshot != null ? options.Snapshot.Sequence : VersionSet.LastSequence;
var iterators = new List<IIterator>
{
mem.NewIterator()
};
if (imm != null)
iterators.Add(imm.NewIterator());
// Merge all level zero files together since they may overlap
iterators.AddRange(currentVersion.Files[0].Select(file => TableCache.NewIterator(options, file.FileNumber, file.FileSize)));
// For levels > 0, we can use a concatenating iterator that sequentially
// walks through the non-overlapping files in the level, opening them
// lazily.
for (var level = 1; level < Config.NumberOfLevels; level++)
{
if (currentVersion.Files[level].Count > 0)
iterators.Add(new TwoLevelIterator(new LevelFileNumIterator(InternalKeyComparator, currentVersion.Files[level]), VersionSet.GetFileIterator, options));
}
var internalIterator = new MergingIterator(InternalKeyComparator, iterators);
return new Tuple<IIterator, ulong>(internalIterator, snapshot);
}
/// <summary>
/// Returns a new iterator over the table contents.
/// The result of NewIterator() is initially invalid (caller must
/// call one of the Seek methods on the iterator before using it).
/// </summary>
public IIterator CreateIterator(ReadOptions readOptions)
{
return new TwoLevelIterator(_indexBlock.CreateIterator(_storageState.Options.Comparator), CreateBlockIterator, readOptions);
}
public Table(StorageState storageState, FileData fileData)
{
_storageState = storageState;
try
{
_fileData = fileData;
if (_storageState.Options.MaxBlockCacheSizePerTableFile > 0)
{
_blockCache = new LruCache<BlockHandle, Block>(_storageState.Options.MaxBlockCacheSizePerTableFile);
}
if (fileData.Size < Footer.EncodedLength)
throw new CorruptedDataException("File is too short to be an sstable");
var footer = new Footer();
using (var accessor = fileData.File.CreateAccessor(fileData.Size - Footer.EncodedLength, Footer.EncodedLength))
{
footer.DecodeFrom(accessor);
}
var readOptions = new ReadOptions
{
VerifyChecksums = _storageState.Options.ParanoidChecks
};
_indexBlock = new Block(_storageState.Options, readOptions, footer.IndexHandle, fileData);
_indexBlock.IncrementUsage();
if (_storageState.Options.FilterPolicy == null)
return; // we don't need any metadata
using (var metaBlock = new Block(_storageState.Options, readOptions, footer.MetaIndexHandle, fileData))
using (var iterator = metaBlock.CreateIterator(CaseInsensitiveComparator.Default))
{
var filterName = ("filter." + _storageState.Options.FilterPolicy.Name);
iterator.Seek(filterName);
if (iterator.IsValid && CaseInsensitiveComparator.Default.Compare(filterName, iterator.Key) == 0)
{
var handle = new BlockHandle();
using (var stream = iterator.CreateValueStream())
{
handle.DecodeFrom(stream);
}
var filterAccessor = _fileData.File.CreateAccessor(handle.Position, handle.Count);
try
{
_filter = _storageState.Options.FilterPolicy.CreateFilter(filterAccessor);
}
catch (Exception)
{
if (_filter == null)
filterAccessor.Dispose();
else
_filter.Dispose();
throw;
}
}
}
}
catch (Exception)
{
Dispose();
throw;
}
}
internal IIterator CreateBlockIterator(ReadOptions readOptions, BlockHandle handle)
{
if (_blockCache == null)
{
Block uncachedBlock = null;
IIterator blockIterator = null;
try
{
uncachedBlock = new Block(_storageState.Options, readOptions, handle, _fileData);
// uncachedBlock.IncrementUsage(); - intentionally not calling this, will be disposed when the iterator is disposed
blockIterator = uncachedBlock.CreateIterator(_storageState.InternalKeyComparator);
return blockIterator;
}
catch (Exception)
{
if (uncachedBlock != null)
uncachedBlock.Dispose();
if (blockIterator != null)
blockIterator.Dispose();
throw;
}
}
Block value;
if (_blockCache.TryGet(handle, out value))
{
return value.CreateIterator(_storageState.InternalKeyComparator);
}
var block = new Block(_storageState.Options, readOptions, handle, _fileData);
block.IncrementUsage(); // the cache is using this, so avoid having it disposed by the cache while in use
_blockCache.Set(handle, block);
return block.CreateIterator(_storageState.InternalKeyComparator);
}
internal Tuple<Slice, Stream> InternalGet(ReadOptions readOptions, InternalKey key)
{
using (var iterator = _indexBlock.CreateIterator(_storageState.InternalKeyComparator))
{
iterator.Seek(key.TheInternalKey);
if (iterator.IsValid == false)
return null;
var handle = new BlockHandle();
using (var stream = iterator.CreateValueStream())
{
handle.DecodeFrom(stream);
}
if (_filter != null && _filter.KeyMayMatch(handle.Position, key.UserKey) == false)
{
return null; // opptimized not found by filter, no need to read the actual block
}
using (var blockIterator = CreateBlockIterator(readOptions, handle))
{
blockIterator.Seek(key.TheInternalKey);
if (blockIterator.IsValid == false)
return null;
return Tuple.Create(blockIterator.Key, blockIterator.CreateValueStream());
}
}
}
