Update node_funs.jl

Optimize reparenting of subtree

Author: VEZY

src/compute_MTG/node_funs.jl

@@ -83,12 +83,45 @@ end
     return _store_for_node_attrs(attrs)
 end
 
+function _subtree_has_node_id_conflict(node::Node, store::MTGAttributeStore)
+    nid = node_id(node)
+    if nid <= length(store.node_bucket) && store.node_bucket[nid] != 0
+        return true
+    end
+    for ch in children(node)
+        _subtree_has_node_id_conflict(ch, store) && return true
+    end
+    return false
+end
+
+function _merge_columnar_subtree_into_store!(node::Node, target_store::MTGAttributeStore)
+    attrs = node_attributes(node)
+    attrs isa ColumnarAttrs || return false
+    snapshot = Dict{Symbol,Any}(pairs(attrs))
+    _add_node_with_attrs!(target_store, node_id(node), symbol(node), snapshot)
+    attrs.ref.store = target_store
+    attrs.ref.node_id = node_id(node)
+    empty!(attrs.staged)
+    for ch in children(node)
+        _merge_columnar_subtree_into_store!(ch, target_store) || return false
+    end
+    return true
+end
+
+function _try_merge_root_subtree_store!(child::Node, parent_store::MTGAttributeStore, child_store::MTGAttributeStore)
+    parent_store === child_store && return true
+    _subtree_has_node_id_conflict(child, parent_store) && return false
+    return _merge_columnar_subtree_into_store!(child, parent_store)
+end
+
 @inline function _maybe_recolumnarize_after_attach!(p::Node, child::Node, child_was_root::Bool)
     child_was_root || return nothing
     p_store = _columnar_store_or_nothing(p)
     c_store = _columnar_store_or_nothing(child)
     if p_store !== nothing && c_store !== nothing && p_store !== c_store
-        columnarize!(get_root(p))
+        # Fast path: re-bind only the attached subtree into the parent store.
+        # Fallback to full re-columnarization when IDs collide.
+        _try_merge_root_subtree_store!(child, p_store, c_store) || columnarize!(get_root(p))
     end
     return nothing
 end