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browser: BrowserDb.open() does not write migrated pages back to IndexedDB #411
Description
Problem
BrowserDb.open() loads all pages from IndexedDB into a BrowserBufferBackend. Then it calls PersistentFactStorage::new(buffer, 0), which runs the normal load path. If the stored data is in an older file format, that load path upgrades it (migrate_v1_to_v2, migrate_v5_to_v6, and the one-per-page repack in load()). The upgrade writes new pages to the buffer and marks them dirty.
open() never sends those dirty pages to IndexedDB. So the upgraded pages only exist in memory. The IndexedDB copy stays in the old format until one of these happens:
- a
transactorretractthroughexecute() - a call to
checkpoint()
import_graph() does not have this problem. It takes the dirty set and writes it right after PersistentFactStorage::new.
Impact
Today this is a latent issue. IndexedDB support shipped in v0.20.0 with format v7, and the format has not changed since. So no existing IndexedDB database needs an upgrade yet.
It will matter when the format changes again (for example #388, format v8):
- A read-only session upgrades the data in memory on every open. The work is repeated each time and the stored copy never changes.
- If the upgrade also fixes a problem in the stored data, such as an index rebuild after a checksum mismatch, that fix is also not saved.
Proposed fix
In BrowserDb::open() (src/browser/mod.rs), after PersistentFactStorage::new(...), do the same thing import_graph() does:
- Call
pfs.with_backend_mut(|b| b.take_dirty()). - Read those pages with
read_page_raw. - If the set is not empty, call
idb.write_pages(...)before returning.
On a normal open with no upgrade, the dirty set is empty, so this adds no IndexedDB write.
Test idea
Add a wasm_bindgen_test that:
- Writes the pages of an older-format fixture (for example a v5 file from test: golden-file compatibility corpus for every file format version #391) straight into an IndexedDB store with
IndexedDbBackend::write_pages. - Opens it with
BrowserDb::open()and runs only a query. - Reads page 0 back from IndexedDB with
load_all_pages()and checks that the header version isFORMAT_VERSION.
Activity
Merge pull request #474 from project-minigraf/fix/411-440-browser-pages
adityamukho commentedon Oct 7, 2026
Fixed on
v3by #474 (merge deb82a4); ships in v3.0.0.