By experimenting I found, that if I delete an item from the bottom of the very first sub-tree in the tree (and therefore nothing should be changed in order sequence), the current code re-sequences all top level nodes.

The problem seems to be in the recursive SaveChild method.


>Hi everybody,
>
>I have a tree view structure, which is stored in this table
>

>select node_id, parent_id, root_id, descrip, sort_order  from ItemTree order by sort_order -- table has more fields, of course

>
>Sort_Order is relevant to the parent_id.
>
>I have the following procedure which is called every time the changes of any type are made to the tree view:
>

>with thisform
>	nChanges   = 0
>	nSortOrder = 1
>* Find a root node in the TreeView
>	oTree = .TList2
>	if oTree.Nodes.count > 0
>		for i = 1 to oTree.Nodes.count
>			oTmp = oTree.Nodes(i).parent
>			if isnull(oTmp) then
>				iTmpIndex = i
>				exit
>			endif
>		next i
>* Get the index of the root node that is at the top of the TreeView
>		iIndex = oTree.Nodes(iTmpIndex).FirstSibling.index
>		iTmpIndex = iIndex
>
>		lnSeekVal = val(substr(oTree.Nodes(iIndex).key, 3))
>		select itemtree
>		set order to node_id
>		seek lnSeekVal
>		if node_id == lnSeekVal and lnSeekVal <> 0
>			if thisform.nBaseRoot_id >= 0
>				nSortOrder = sort_order
>			else
>				if sort_order <> nSortOrder
>					replace sort_order with nSortOrder
>					nChanges = nChanges + 1
>					.lUpdateItemTree = .t.
>				endif
>			endif
>		else
>			.log("Seek Failed on node id:" + oTree.Nodes(iIndex).key, program(), 1)
>		endif
>
>* If the Node has Children call the sub that writes the children
>		if oTree.Nodes(iIndex).Children > 0
>			nChanges = nChanges + .SaveChild(iIndex)
>		endif
>
>		do while iIndex <> oTree.Nodes(iTmpIndex).LastSibling.index
>*Loop through all the root nodes
>			nSortOrder = nSortOrder + 1
>			lnSeekVal  = val(substr(oTree.Nodes(iIndex).next.key, 3))
>			select itemtree
>			seek lnSeekVal
>			if node_id == lnSeekVal and lnSeekVal <> 0
>				if sort_order <> nSortOrder
>					replace sort_order with nSortOrder
>					nChanges = nChanges + 1
>					.lUpdateItemTree = .t.
>				endif
>			else
>				.log("Seek Failed on node id:" + oTree.Nodes(iIndex).next.key, program(), 1)
>			endif
>			if oTree.Nodes(iIndex).next.Children > 0
>				nChange = nChanges + .SaveChild(oTree.Nodes(iIndex).next.index)
>			endif
>			iIndex = oTree.Nodes(iIndex).next.index
>		enddo
>	endif
>	.log("Total number of changed records in the Item tree: " + alltrim(transform(m.nChanges,'@999,999,999')), program(), 1)
>endwith
>
>return nChanges
>

>
>I found that even if I add a new item to the very bottom of one of the subtrees (and so I should not change more than 1 item), I still end up with the lots of changes.
>
>I'm wondering if this algorithm can be improved to minimize number of changes written in the database?
>
>Thanks a lot in advance for the suggestions.