Pure OCaml B-tree implementation for persistent storage
btree: Fix interior page insert when inserting in middle
When inserting a separator into an interior page at position i < cell_count,
the displaced cell (now at i+1) must have its left_child updated to point
to right_child. Previously, only the page's right_child was updated when
inserting at the end.
This fixes lookups failing after multiple splits with non-sequential
insertion order (e.g., reverse or random).
+14
-2
+14
-2
lib/btree.ml
+14
-2
lib/btree.ml
···
760
760
(* Update cell count *)
761
761
set_u16_be buf 3 (header.cell_count + 1);
762
762
763
-
(* Update right child if inserting at end *)
764
-
if insert_idx = header.cell_count then set_u32_be buf 8 right_child;
763
+
(* Update child pointers: the cell we displaced (now at insert_idx+1)
764
+
needs its left_child updated to right_child, OR if we inserted at end,
765
+
update the page's right_child. *)
766
+
if insert_idx < header.cell_count then begin
767
+
(* Update the displaced cell's left_child to right_child *)
768
+
let ptr_start = page_header_size Interior_table in
769
+
let displaced_ptr =
770
+
get_u16_be
771
+
(Bytes.unsafe_to_string buf)
772
+
(ptr_start + ((insert_idx + 1) * 2))
773
+
in
774
+
set_u32_be buf displaced_ptr right_child
775
+
end
776
+
else set_u32_be buf 8 right_child;
765
777
766
778
Pager.write t.pager page_num (Bytes.unsafe_to_string buf);
767
779
None