>>Maybe I'm missing something but why do all this.
>>If a node in the treeview changes just find the relevant record and update it accordingly ?
>>
>
>The data updates are done, no problem. But what about re-sequencing? In other words, if you insert a node in the middle or remove a node in the middle, you need to re-sequence nodes in that particular branch.
>
>Now, the re-sequencing happens at the very end, when we're saving all the modifications made. The user could have done many modifications. So, by traversing the tree we're comparing the current order of each node with the SortOrder in the ItemTree table and adjust the Order if necessary.
>
>My problem is, that this process does extra changes - I want to do only the necessary (minimum changes).
But if a node changes position it will only affect the sort order of its current/new siblings. Can't you just loop through the children of its parent node and reorder those (if it's moved to a different parent node you shouldn't have to worry about re-ordering its *ex*-siblings)
FWIW, IIRC, the last time I did this (with approx 200-300 nodes in total) I simple read the whole table into the tree and wrote the entire thing out again afterwards. Overkill when there were only a few changes but made sense when the user was likely to make a lot of changes in one session but it avoided the whole problem of keeping the data records in sync with the tree.
>>>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.
