/// <summary>
/// Attempts to ensure that the minimum size for this node is achieved by transferring entries from the left-hand sibling
/// </summary>
/// <param name="txnId"></param>
/// <param name="leftSibling">The left-hand sibling that will provide entries</param>
/// <param name="joinKey">The value of the key that is present in the parent node between the pointer to this node and its left sibling</param>
/// <param name="newJoinKey">The replacement value for the join key in the parent node</param>
/// <returns>True if the node achieves its minimum size by the redistribution process, false otherwise</returns>
public bool RedistributeFromLeft(ulong txnId, IInternalNode leftSibling, byte[] joinKey, byte[] newJoinKey)
{
InternalNode left = leftSibling as InternalNode;
if (left == null)
{
throw new ArgumentException("Expected a InternalNode as left sibling", "leftSibling");
}
int required = _config.InternalSplitIndex - KeyCount;
if (leftSibling.KeyCount - required < _config.InternalSplitIndex)
{
// Can't fulfill requirements with a borrow from left sibling
return(false);
}
int evenOut = (KeyCount + left.KeyCount) / 2 - KeyCount;
if (leftSibling.KeyCount - evenOut > _config.InternalSplitIndex)
{
required = evenOut;
}
EnsureWriteable(txnId);
left.EnsureWriteable(txnId);
// Make space for new keys and child pointers
RightShift(required);
_page.SetData(joinKey, 0, KeyOffset(required - 1), _config.KeySize);
_page.SetData(left.GetData(), KeyOffset(left.KeyCount - (required - 1)),
KeyOffset(0), (required - 1) * _config.KeySize);
_page.SetData(left.GetData(), PointerOffset(left.KeyCount - (required - 1)),
PointerOffset(0), (required) * 8);
Array.Copy(left.GetData(), KeyOffset(left.KeyCount - required), newJoinKey, 0, _config.KeySize);
KeyCount += required;
left.KeyCount -= required;
return(true);
}
private KeyValuePair <byte[], ulong> WriteNode(ulong txnId, InternalNode node, byte[] lowestLeafKey, BrightstarProfiler profiler)
{
_pageStore.Write(txnId, node.PageId, node.GetData(), profiler: profiler);
return(new KeyValuePair <byte[], ulong>(lowestLeafKey, node.PageId));
}
private KeyValuePair<byte[], ulong > WriteNode(ulong txnId, InternalNode node, byte[] lowestLeafKey, BrightstarProfiler profiler)
{
_pageStore.Write(txnId, node.PageId, node.GetData(), profiler:profiler);
return new KeyValuePair<byte[], ulong>(lowestLeafKey, node.PageId);
}
