private byte *SplitPageInHalf(Page rightPage)
{
bool toRight;
var currentIndex = _page.LastSearchPosition;
var splitIndex = _page.NumberOfEntries / 2;
if (currentIndex <= splitIndex)
{
toRight = false;
}
else
{
toRight = true;
var leftPageEntryCount = splitIndex;
var rightPageEntryCount = _page.NumberOfEntries - leftPageEntryCount + 1;
if (rightPageEntryCount > leftPageEntryCount)
{
splitIndex++;
Debug.Assert(splitIndex < _page.NumberOfEntries);
}
}
PrefixNode[] prefixes = null;
if (_tree.KeysPrefixing && _page.HasPrefixes)
{
prefixes = _page.GetPrefixes();
}
if (_page.IsLeaf || prefixes != null)
{
splitIndex = AdjustSplitPosition(currentIndex, splitIndex, prefixes, ref toRight);
}
var currentKey = _page.GetNodeKey(splitIndex);
MemorySlice seperatorKey;
if (toRight && splitIndex == currentIndex)
{
seperatorKey = currentKey.Compare(_newKey) < 0 ? currentKey : _newKey;
}
else
{
seperatorKey = currentKey;
}
Page parentOfRight;
AddSeparatorToParentPage(rightPage.PageNumber, seperatorKey, out parentOfRight);
var parentOfPage = _cursor.CurrentPage;
MemorySlice instance = _page.CreateNewEmptyKey();
if (prefixes != null)
{
for (int i = 0; i < prefixes.Length; i++)
{
var prefix = prefixes[i];
rightPage.WritePrefix(new Slice(prefix.ValuePtr, prefix.PrefixLength), i);
}
}
bool addedAsImplicitRef = false;
if (_page.IsBranch && toRight && seperatorKey == _newKey)
{
// _newKey needs to be inserted as first key (BeforeAllKeys) to the right page, so we need to add it before we move entries from the current page
AddNodeToPage(rightPage, 0, _tree.KeysPrefixing ? (MemorySlice)PrefixedSlice.BeforeAllKeys : Slice.BeforeAllKeys);
addedAsImplicitRef = true;
}
// move the actual entries from page to right page
ushort nKeys = _page.NumberOfEntries;
for (int i = splitIndex; i < nKeys; i++)
{
NodeHeader *node = _page.GetNode(i);
if (_page.IsBranch && rightPage.NumberOfEntries == 0)
{
rightPage.CopyNodeDataToEndOfPage(node, _tree.KeysPrefixing ? (MemorySlice)PrefixedSlice.BeforeAllKeys : Slice.BeforeAllKeys);
}
else
{
_page.SetNodeKey(node, ref instance);
var key = rightPage.PrepareKeyToInsert(instance, rightPage.NumberOfEntries);
rightPage.CopyNodeDataToEndOfPage(node, key);
}
}
_page.Truncate(_tx, splitIndex);
byte *pos;
if (addedAsImplicitRef == false)
{
try
{
if (toRight && _cursor.CurrentPage.PageNumber != parentOfRight.PageNumber)
{
// modify the cursor if we are going to insert to the right page
_cursor.Pop();
_cursor.Push(parentOfRight);
}
// actually insert the new key
pos = toRight ? InsertNewKey(rightPage) : InsertNewKey(_page);
}
catch (InvalidOperationException e)
{
if (e.Message.StartsWith("The page is full and cannot add an entry") == false)
{
throw;
}
throw new InvalidOperationException(GatherDetailedDebugInfo(rightPage, currentKey, seperatorKey, currentIndex, splitIndex, toRight), e);
}
}
else
{
pos = null;
_cursor.Push(rightPage);
}
if (_page.IsBranch) // remove a branch that has only one entry, the page ref needs to be added to the parent of the current page
{
Debug.Assert(_page.NumberOfEntries > 0);
Debug.Assert(rightPage.NumberOfEntries > 0);
if (_page.NumberOfEntries == 1)
{
RemoveBranchWithOneEntry(_page, parentOfPage);
}
if (rightPage.NumberOfEntries == 1)
{
RemoveBranchWithOneEntry(rightPage, parentOfRight);
}
}
return(pos);
}