Make the corpus figures cheap enough to ever appear

[ralyodio]

Found by looking at the live page after #163 deployed: /sales was showing three of its five figures. Full-text articles and Authors were missing, and would have stayed missing.

What happened

articleFigures sampled 20,000 rows to compute an average article length. text_length is covered by no index, so the cost is one row lookup per sampled row and nothing else. Measured against production, 2026-08-29:

query	time	result
count(*) where status='ok'	1,946ms	274,885
avg over 20,000	22,662ms	7,810
avg over 2,000	584ms	7,929
count(*) from authors	695ms	195,456

Twenty-three seconds against a caller timeout of eight. The read failed — and remember stores nothing on failure, which is exactly the trap cache.js was written to describe:

a "compute on miss, store on success" cache stores nothing, and every single request pays 30 seconds forever

So it does not fail once and recover. It fails for ever. The page rendered its graceful fallback (rows omitted rather than showing zeroes) permanently, which is why nothing looked broken — the fallback worked exactly as designed.

The fix

Sample 2,000 instead of 20,000. Ten times the sample bought a difference of 1.5% on a figure already labelled "sampled" on the page, against 39 times the cost and a page that could not show it at all.

Timeout also raised from 8s to 15s against ~3s of measured work. A timeout under the cost of the work it guards is not a safety margin, it is an off switch with a delay on it. Paid only on a genuinely cold cache; one success by anyone serves every reader for an hour.

If a defensible exact total is ever wanted, the answer is a sum(text_length) warmed by the poller on its patient connection — not a bigger sample on the request path.

Test

Bounds the sample (<= 5_000) rather than pinning it. The number is a judgement call and may reasonably move; the order of magnitude is not. Raising it past the bound does not make the page slow, it makes it empty — so the assertion message points at the measurement.

Full suite green on Node 22, pnpm build clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Pij2tFcRgqceMpheotFSoX