iotaledger / iota / 34003649292

70%

Build Type

push

github

Committed by web-flow

Commit Message

refactor(typed-store): make the lower bound of prefix scans exclusive-capable (#12831)

# Description of change

`DBMap::safe_iter_with_prefix_from(prefix, cursor)` can resume a prefix
scan only *at* the cursor: the start key is always included. Every
caller that needs "strictly after the cursor" (a paginated reader
resuming from the last row it returned) emulates that on its own:
`skip(1)` on the result stream (gRPC readers for owned objects, dynamic
fields and package versions), `cursor.unwrap_or(ObjectId::ZERO)` plus
`skip` (JSON-RPC dynamic-field index), a hand-rolled
`version.next().unwrap()` (authority store).

This PR makes the lower bound a `Bound<&C>`, so a caller states
`Included`, `Excluded` or `Unbounded` explicitly. `Excluded` reuses the
existing byte-successor logic of `prefix_iterator_bounds_with_range`;
the scan never leaves the prefix, including for a cursor whose tail is
all `0xFF` (the successor of the tail alone would sort past the prefix,
but the upper bound at the end of the prefix cuts it off; covered by a
unit test).

Along the way, `prefix_iterator_bounds` (whole prefix) becomes a thin
wrapper over `prefix_iterator_bounds_with_range` (prefix plus a range
over the key tail): the former is the `..` special case of the latter.
Previously the dependency ran the other way and the prefix was
serialized twice on the unbounded-upper path.

`safe_iter_with_prefix_after(prefix, cursor: Option<&C>)` names the one
form paginated readers need (strictly after the cursor, or the whole
prefix without one), so they pass the cursor directly instead of mapping
it onto a `Bound`.

Pure refactor: every existing call site is updated mechanically to
`Bound::Included(<old argument>)` and behaves exactly as before.
Switching the paginated readers to `Excluded`, which is what removes
their `skip(1)` and the bug it hides, is done in #12832.

Not in this PR:

- `package_versions_iter` (gRPC) and JSON-RPC
`IndexStore::get_dynamic_fields_iterator` move to ... (continued)

Coverage Stats

35 of 38 new or added lines in 5 files covered. (92.11%)

138 existing lines in 12 files now uncovered.

178495 of 253026 relevant lines covered (70.54%)

442632.9 hits per line