public ResultStatus Get(Span <byte> key)
{
if (Log.IsDebugEnabled)
{
Log.Debug($"\nSearch Key={key.ToHexString()}");
}
// To find a key in the table you:
// 1) Read the block index. This index have one entry for each block in the file. For each entry it holds the
// last index and a block handle for the block. Binary search this and find the correct block.
// 2) Search either each entry in the block (brute force) OR use the restart index at the end of the block to find an entry
// closer to the index you looking for. The restart index contain a subset of the keys with an offset of where it is located.
// Use this offset to start closer to the key (entry) you looking for.
// 3) Match the key and return the data
// Search block index
if (_blockIndex == null || _metaIndex == null)
{
Footer footer;
using (MemoryMappedViewStream stream = _memFile.CreateViewStream(_file.Length - Footer.FooterLength, Footer.FooterLength, MemoryMappedFileAccess.Read))
{
footer = Footer.Read(stream);
}
_blockIndex = footer.BlockIndexBlockHandle.ReadBlock(_memFile);
_metaIndex = footer.MetaindexBlockHandle.ReadBlock(_memFile);
}
BlockHandle handle = FindBlockHandleInBlockIndex(key);
if (handle == null)
{
Log.Error($"Expected to find block, but did not");
return(ResultStatus.NotFound);
}
if (_bloomFilterPolicy == null)
{
var filters = GetFilters();
if (filters.TryGetValue("filter.leveldb.BuiltinBloomFilter2", out BlockHandle filterHandle))
{
//var filterBlock = filterHandle.ReadBlock(_memViewStream);
var filterBlock = filterHandle.ReadBlock(_memFile);
if (Log.IsDebugEnabled)
{
Log.Debug("\n" + filterBlock.HexDump(cutAfterFive: true));
}
_bloomFilterPolicy = new BloomFilterPolicy();
_bloomFilterPolicy.Parse(filterBlock);
}
}
if (_bloomFilterPolicy?.KeyMayMatch(key, handle.Offset) ?? true)
{
var targetBlock = GetBlock(handle);
return(SeekKeyInBlockData(key, targetBlock));
}
return(ResultStatus.NotFound);
}
internal void Initialize()
{
if (_initialized)
{
return;
}
if (_blockIndex == null || _metaIndex == null)
{
Log.Debug($"Initialize table {_file.Name}");
Footer footer;
using (MemoryMappedViewStream stream = _memFile.CreateViewStream(_file.Length - Footer.FooterLength, Footer.FooterLength, MemoryMappedFileAccess.Read))
{
footer = Footer.Read(stream);
}
_blockIndex = footer.BlockIndexBlockHandle.ReadBlock(_memFile);
_metaIndex = footer.MetaIndexBlockHandle.ReadBlock(_memFile);
Log.Debug($"initialized table index len {_blockIndex?.Length}");
Dictionary <string, BlockHandle> filters = GetFilters();
if (filters.TryGetValue("filter.leveldb.BuiltinBloomFilter2", out BlockHandle filterHandle))
{
byte[] filterBlock = filterHandle.ReadBlock(_memFile);
if (Log.IsDebugEnabled)
{
Log.Debug("Found filter block:\n" + filterBlock.HexDump(cutAfterFive: true));
}
_bloomFilterPolicy = new BloomFilterPolicy();
_bloomFilterPolicy.Parse(filterBlock);
}
_initialized = true;
}
}