Building an end-to-end integration test (mock grin node → real tick() →
SQLite store) surfaced the real dual-DB blockers in sqlx::Any — NOT the
placeholder issue the review flagged:
- Any truncates i64 -> i32 for SQLite (12345678900 -> -539222988),
which would corrupt grin amounts. Store outputs.value as a decimal
string, sum in Rust. (Probe-documented; other int columns are < 2^31
for decades.)
- Any can't decode SQLite BOOLEAN; is_coinbase/spent are now INTEGER 0/1.
- DEFAULT now() -> DEFAULT CURRENT_TIMESTAMP (portable).
The integration test now proves the whole pipeline end-to-end on SQLite:
node UTXO listing → view-only rewind (golden output) → store with
value + key_id → correct balance → spend-by-absence reconcile → zero.
One schema + one query set now serve both backends.
The review's premise (sqlx::Any breaks on SQLite $N placeholders) is
wrong for sqlx 0.7: SQLite accepts $N numbered params and binds them
positionally, including reused placeholders. A probe test applies the
real migration + exercises set_cursor's reused-$N upsert, insert_output
(quoted "commit", bool), coinbase-maturity reads, and mark_spent against
SQLite — all pass. The only true incompatibility was DEFAULT now(),
changed to the portable DEFAULT CURRENT_TIMESTAMP. Schema + queries now
run unchanged on both backends. Updated the stale dialect notes.
Replace the stub scanner with the real incremental algorithm:
- discover: page get_unspent_outputs (with proofs) from the cursor to
the tip, rewind each new output against caught-up accounts, store
matches with their derivation path + a derived lock_height (coinbase
maturity = 1440)
- spend reconcile: mark any stored-unspent commit the node no longer
lists (grin has no per-block inputs; spends = absence from the set)
- reorg: detect via header-hash mismatch at the checkpoint height,
roll back a bounded depth, reseek from the fork
- backfill: bring a newly-registered account up from its birthday index
- cursor only advances after discover AND reconcile succeed
DB: chain_cursor gains output_mmr_index (tip height/hash become the
reorg checkpoint); new helpers (list_accounts, all_unspent_commits,
mark_unspent, account_unlocked_totals, scan-height advance/clamp).
Read path: get_balance adds `unlocked` (spendable-now) and
get_unspent_outs flags per-output `spendable`, so immature coinbase /
locked outputs are never presented as spendable.
A standalone, self-hostable Grin light-wallet-server mirroring the Monero LWS:
register a view/rewind credential, run a background chain scanner, rewind outputs
against registered keys, store per-account matches in a DB, and serve balance /
outputs / broadcast / height fast (vs the current on-demand stateless scan proxy).
This is the scaffold — README (architecture + HTTP surface + DB schema + how a
wallet backend proxies to it), Cargo skeleton, migrations sketch, and route/scanner
stubs. Public-clean: no operator-specific infra, hosts, or secrets.
jwinterm