public SequenceSize ReadNext(ReadOnlySequence <byte> sequence)
{
if (_baseReader != null)
{
var result = _baseReader.ReadNext(sequence);
return(result);
}
var prefixBytesCount = _rowCount - _position;
if (prefixBytesCount < 0)
{
throw new ClickHouseException(ClickHouseErrorCodes.DataReaderError, "Internal error. Attempt to read after the end of the column.");
}
if (sequence.Length <= prefixBytesCount)
{
_position += (int)sequence.Length;
return(new SequenceSize((int)sequence.Length, 0));
}
else
{
_position += prefixBytesCount;
}
_baseReader = _underlyingType.CreateSkippingColumnReader(_rowCount);
var baseSize = _baseReader.ReadNext(sequence.Slice(prefixBytesCount));
return(new SequenceSize(baseSize.Bytes + prefixBytesCount, baseSize.Elements));
}
public SequenceSize ReadNext(ReadOnlySequence <byte> sequence)
{
var slice = sequence;
var result = new SequenceSize(0, 0);
if (_baseReader == null)
{
var header = LowCardinalityColumnReader.TryReadHeader(slice);
if (header == null)
{
return(result);
}
result = result.AddBytes(header.Value.bytesRead);
slice = slice.Slice(header.Value.bytesRead);
_baseRowCount = header.Value.keyCount;
_keySize = header.Value.keySize;
_baseReader = _baseType.CreateSkippingColumnReader(_baseRowCount);
}
if (_basePosition < _baseRowCount)
{
var baseResult = _baseReader.ReadNext(slice);
_basePosition += baseResult.Elements;
result = result.AddBytes(baseResult.Bytes);
if (_basePosition < _baseRowCount)
{
return(result);
}
}
if (!_headerSkipped)
{
if (sequence.Length - result.Bytes < sizeof(ulong))
{
return(result);
}
ulong length = 0;
sequence.Slice(result.Bytes, sizeof(ulong)).CopyTo(MemoryMarshal.AsBytes(MemoryMarshal.CreateSpan(ref length, 1)));
if ((int)length != _rowCount)
{
throw new ClickHouseException(ClickHouseErrorCodes.DataReaderError, $"Internal error. Row count check failed: {_rowCount} rows expected, {length} rows detected.");
}
result = result.AddBytes(sizeof(ulong));
_headerSkipped = true;
}
var maxElementsCount = _rowCount - _position;
if (maxElementsCount <= 0)
{
throw new ClickHouseException(ClickHouseErrorCodes.DataReaderError, "Internal error. Attempt to read after the end of the column.");
}
var elementCount = (int)Math.Min((sequence.Length - result.Bytes) / _keySize, maxElementsCount);
_position += elementCount;
result += new SequenceSize(elementCount * _keySize, elementCount);
return(result);
}