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H6: migration 006 replaces v_feed's double LEFT JOIN + COUNT(DISTINCT) (which materialized a likes×comments Cartesian per upload) with correlated scalar subqueries that each use their own index. Output columns are unchanged, so feed + hashtag-filtered paths both benefit. H7: feed_delta now applies the feed rate limit (keyed per user), caps results at 200 rows, and clamps how far back a client `since` may reach (7 days). When clamped or capped it returns reload_required=true; the SSE client turns that into a full feed reload instead of streaming the whole gallery through the view on every tab refocus. M9: the SSE reconnect cursor is now advanced only from server timestamps (an upload's created_at, seeded from the feed and updated on new-upload events and delta responses), never the client clock — so a skewed phone clock can't drop events missed while backgrounded. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Migrations
SQLx-managed Postgres migrations. Each NNN_topic.up.sql has a matching
NNN_topic.down.sql. Run by sqlx::migrate!() at app start.
Rules
- Never edit a shipped migration. If a column needs to change or a fix needs to land, write a new migration. Production has already applied the old one and SQLx tracks each by checksum — editing in place will fail to apply on existing databases.
- Always pair
.up.sqlwith a.down.sql. Reverts may not be perfect (data loss is sometimes unavoidable) but the file must exist and do the best it can. - Prefer additive changes. New columns, new tables, new keys in
config. Drop / rename only when there is no alternative. - No business logic in migrations. Schema + seeds only. Anything that needs Rust code goes in a one-off binary, not a migration file.
- One concern per migration. Easier to revert. Easier to read in
git log.
Numbering
Zero-padded three digits, monotonically increasing. The next free number lives at the bottom of the directory listing — pick that.
Seed-only migrations
When you only need to add config keys (feature flags, defaults), use
INSERT … ON CONFLICT DO NOTHING so existing operator overrides survive. See
009_feature_toggles.up.sql for the canonical shape.