efitenandClaude Opus 5.5 a2b5a4931e perf(server): battery history via the primary key, cached /api/perf row counts (#2156) ...

Refs #2146 (items: `/api/nodes/:pubkey/battery`, `/api/perf`).

## Situation

Two endpoints ran SQL that reads more than it needs, on every request.
Timings are read-only on a production database (18.3M observations, 283k
`observer_metrics` rows), first run / second run:

| Query | Now | With this PR |
|---|---|---|
| battery history, `WHERE LOWER(observer_id) = ?` | 174 / 29 ms (plan:
`idx_observer_metrics_timestamp`) | 5.9 / 5.5 ms (plan: primary key
`(observer_id, timestamp)`) |
| `/api/perf`: `SELECT COUNT(*) FROM observations` | 118 / 116 ms on
every call | once per 60 s |

## My changes in this PR

1. **Battery history** (`5bdd3c7f`). `LOWER(observer_id) = ?` keeps
SQLite off the primary-key index, so it walked the timestamp index over
every observer's metrics in the window. The query now matches
`observer_id IN (?, ?)` with the pubkey lowercased and uppercased, the
two casings observer IDs are stored in.
2. **`/api/perf` row counts** (`e24c24cf`). The four `COUNT(*)`
(transmissions, observations, nodes, observers) are cached for 60 s.
File, WAL and freelist sizes are still read on every call.

## Tests

- `TestNodeBatteryQueryUsesObserverIndex` loads the `sqlite_stat1`
values of that database and checks the plan uses
`sqlite_autoindex_observer_metrics_1`. With the `LOWER()` form it fails
with `SEARCH observer_metrics USING INDEX idx_observer_metrics_timestamp
(timestamp>?)`.
- `TestGetNodeBatteryHistory_LowercaseStoredID`: a lowercase-stored
observer ID is still found.
- `TestGetDBSizeStatsTypedCachesRowCounts`: the cached count is served
within the TTL and refreshed after it.
- `cmd/server`: `go test ./...` green.

## Not in this PR

Other per-request queries listed in #2146 measured too small to change
on the same database: `COUNT(*) FROM dropped_packets` 0.0 ms, `SELECT
DISTINCT iata FROM observers` 0.2 ms, the observers packet-count query
1.3 ms, the 7-day active node count 0.1 ms. An observer ID stored in
mixed case would no longer match the battery query; in that database all
41 distinct `observer_metrics.observer_id` values are uppercase.

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

2026-10-10 11:03:56 +02:00

..

decrypt

perf(sqlite): swap modernc.org/sqlite for mattn/go-sqlite3, cross-built with zig (#1992)

2026-09-16 09:02:13 +02:00

ingestor

feat: propose and approve hashtag channels (user management part D) (#2139)

2026-10-08 21:51:42 +02:00

migrate

perf(sqlite): swap modernc.org/sqlite for mattn/go-sqlite3, cross-built with zig (#1992)

2026-09-16 09:02:13 +02:00

server

perf(server): battery history via the primary key, cached /api/perf row counts (#2156)

2026-10-10 11:03:56 +02:00