docs(postgres): add major version upgrade guide

[paulocsanz]

Summary

• Adds a guide for the in-place PostgreSQL major-version upgrade flow (preflight report, backup/revert, HA-cluster behavior) — the feature had no documentation.
• Cross-links it from the standalone PostgreSQL and Postgres HA guides.

Test plan

• Content reviewed for accuracy against the shipped major-upgrade feature (preflight checks, revert banner, manual-image-edit warning — all verified against current frontend/backend source)
• Renders correctly in the docs site preview

[rw-growth-check]

Growth check — AMH estimate

#1310 @ bc871a9 — advisory only. Judgment ranges, ≤2 significant figures; SEO and AEO legs are never summed (AMH_RULES v2.2, constants v2.3 (2026-08-06)).

Files considered:

• content/docs/databases/postgresql-ha.md (modified)
• content/docs/databases/postgresql-major-upgrade.md (added)
• content/docs/databases/postgresql.md (modified)

SEO leg (Google surface)

2.5–8.5 visits/mo

AEO leg (AI assistants)

1.2–3.5 visits/mo

Gates

• SERP page type(s): unknown
• AI Overview present: absent
• Gated to zero: no
• Gauge topic: database-and-search-deployment (matched)

Keyword candidates for the AMH panel

New (not yet curated) deploy/hosting-intent keywords found around this content — candidates to add to the panel/Gauge:

Keyword	US volume/mo	KD	Question
postgresql major version upgrade methods	20	—	no
postgresql major version upgrade	10	—	no
postgresql backup and recovery	10	—	no
postgresql major version upgrade pg_upgrade	10	—	no
postgresql major version upgrade best practices	0	—	no
best way to upgrade postgresql major version	0	—	no
postgresql upgrade major version	0	—	no
postgresql major version upgrade from 16 to 17	0	—	no
safest method to upgrade postgresql major version	0	—	no
postgresql pg_upgrade for major version upgrade	0	—	no

Caveats & verification stamps

• Current-traffic baseline (modified pages): /databases/postgresql-ha: 109 pageviews, 84 visitors (2 AI-referred) over ~2mo; /databases/postgresql: 1133 pageviews, 879 visitors (18 AI-referred) over ~2mo; /deploy/postgresql: 149 pageviews, 139 visitors (0 AI-referred) over ~2mo.
• Verification pass: PostHog rates are stamped person- vs event-level — visitors are person-level (uniqExact person_id), pageviews are event-level (AMH_RULES §5/§8).
• SERP page-type gate could not be evaluated (no SERP page-type data) — verify winnability manually before pricing (AMH_RULES §2.2).
• Verification pass: the AEO Δ is a labeled ASSUMPTION (+1pt; caps +2 pts/quarter, +6 pts/12mo — AMH_RULES §3.5).

How to go deeper

Ask an agent with the railway-internal MCP (the gauge_* / ahrefs_* / posthog_* tools) or the amh-growth skill for observed-anchor pricing, live SERP inspection, topic curation, and citation checks.

Ahrefs cost: 1799 API units · How AMH is calculated

[railway-app]

🚅 Deployed to the docs-pr-1310 environment in 🪄 *.railway.com

Service	Status	Web	Updated (UTC)
Docs Frontend	✅ Success (View Logs)	Web	Aug 26, 2026 at 1:25 pm

6 services not affected by this PR

• devicons
• OG
• Frontend Redis
• Turnout
• Meilisearch
• Geofeed