Khalim Conn-Kowlessar 9bf36ad4b6 perf(backfill): faster, resumable recommendation denormalization + ops tooling ... Overhaul the recommendation plan_id/material_* backfill for the 21M-row prod table (see docs/runbooks/recommendation-denormalization-backfill.md): - Single combined pass: set plan_id + all four material_* columns in one write per row (was two full passes, rewriting every row twice). Guard + COALESCE keep it idempotent and resumable — done rows are never rewritten. - Session tuning: synchronous_commit=off, tunable work_mem / maintenance_work_mem. - Range + phase controls (BACKFILL_START_ID/END_ID/SKIP_CARDINALITY/ONLY_FINALIZE) to run disjoint id-range workers in parallel when the disk isn't the bottleneck. - Percent-complete + ETA in the progress log. - Finalize builds the two new indexes plain by default (faster in a quiet window) with a CONCURRENTLY toggle. The real speed-up in prod was dropping the 3 secondary indexes for the backfill then rebuilding — the table is packed (fillfactor 100) so updates can't go HOT and otherwise maintain every index per row. Index drop/rebuild + vacuum are kept as standalone SQL so ops controls exactly when the app loses/regains them: - sql/drop-recommendation-backfill-indexes.sql - sql/rebuild-recommendation-backfill-indexes.sql (1GB maintenance_work_mem — safe on the 4GB instance) - sql/vacuum-recommendation.sql run-sql.ts runs .sql files statement-by-statement, autocommitted (so VACUUM / CREATE INDEX CONCURRENTLY work), for environments without the psql CLI. Wired up as npm run db:run-sql and backfill:recommendation-restore. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>		2026-07-02 10:00:46 +00:00
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recommendation-denormalization-backfill.md	perf(backfill): faster, resumable recommendation denormalization + ops tooling	2026-07-02 10:00:46 +00:00