/// <summary>
/// Go first/last occurence of this index value
/// </summary>
private IndexNode FindBoundary(CollectionIndex index, IndexNode cur, BsonValue value, int order, int level)
{
var last = cur;
while (cur.Key.CompareTo(value) == 0)
{
last = cur;
cur = this.GetNode(cur.NextPrev(0, order));
if (cur.IsHeadTail(index))
{
break;
}
}
return(last);
}
/// <summary>
/// Create a new index and returns head page address (skip list)
/// </summary>
public CollectionIndex CreateIndex(CollectionPage col)
{
// get index slot
var index = col.GetFreeIndex();
// get a new index page for first index page
var page = _pager.NewPage <IndexPage>();
// create a empty node with full max level
var head = new IndexNode(IndexNode.MAX_LEVEL_LENGTH)
{
Key = BsonValue.MinValue,
KeyLength = (ushort)BsonValue.MinValue.GetBytesCount(false),
Page = page,
Position = new PageAddress(page.PageID, 0)
};
// add as first node
page.Nodes.Add(head.Position.Index, head);
// update freebytes + item count (for head)
page.UpdateItemCount();
_pager.SetDirty(index.Page);
// add indexPage on freelist if has space
_pager.AddOrRemoveToFreeList(true, page, index.Page, ref index.FreeIndexPageID);
// point the head/tail node to this new node position
index.HeadNode = head.Position;
// insert tail node
var tail = this.AddNode(index, BsonValue.MaxValue, IndexNode.MAX_LEVEL_LENGTH);
index.TailNode = tail.Position;
return(index);
}
/// <summary>
/// Insert a new node index inside an collection index.
/// </summary>
private IndexNode AddNode(CollectionIndex index, BsonValue key, byte level)
{
// calc key size
var keyLength = key.GetBytesCount(false);
if (keyLength > MAX_INDEX_LENGTH)
{
throw LiteException.IndexKeyTooLong();
}
// creating a new index node
var node = new IndexNode(level)
{
Key = key,
KeyLength = (ushort)keyLength
};
// get a free page to insert my index node
var page = _pager.GetFreePage <IndexPage>(index.FreeIndexPageID, node.Length);
node.Position = new PageAddress(page.PageID, page.Nodes.NextIndex());
node.Page = page;
// add index node to page
page.Nodes.Add(node.Position.Index, node);
// update freebytes + items count
page.UpdateItemCount();
// now, let's link my index node on right place
var cur = this.GetNode(index.HeadNode);
// using as cache last
IndexNode cache = null;
// scan from top left
for (var i = IndexNode.MAX_LEVEL_LENGTH - 1; i >= 0; i--)
{
// get cache for last node
cache = cache != null && cache.Position.Equals(cur.Next[i]) ? cache : this.GetNode(cur.Next[i]);
// for(; <while_not_this>; <do_this>) { ... }
for (; cur.Next[i].IsEmpty == false; cur = cache)
{
// get cache for last node
cache = cache != null && cache.Position.Equals(cur.Next[i]) ? cache : this.GetNode(cur.Next[i]);
// read next node to compare
var diff = cache.Key.CompareTo(key);
// if unique and diff = 0, throw index exception (must rollback transaction - others nodes can be dirty)
if (diff == 0 && index.Options.Unique)
{
throw LiteException.IndexDuplicateKey(index.Field, key);
}
if (diff == 1)
{
break;
}
}
if (i <= (level - 1)) // level == length
{
// cur = current (imediatte before - prev)
// node = new inserted node
// next = next node (where cur is poiting)
_pager.SetDirty(cur.Page);
node.Next[i] = cur.Next[i];
node.Prev[i] = cur.Position;
cur.Next[i] = node.Position;
var next = this.GetNode(node.Next[i]);
if (next != null)
{
_pager.SetDirty(next.Page);
next.Prev[i] = node.Position;
}
}
}
// add/remove indexPage on freelist if has space
_pager.AddOrRemoveToFreeList(page.FreeBytes > IndexPage.INDEX_RESERVED_BYTES, page, index.Page, ref index.FreeIndexPageID);
return(node);
}