Engineering Blog

Engineering deep-dives from the SlashFeed team — Elixir, Phoenix, and how the product is built.

all a11y accessibility ai api architecture authentication automations beam blog boruta browserless build-in-public cassandra circuit-breaker claude cron css css-selectors databases debugging discovery dns dnsmasq documentation driver-js ecto elixir fido2 finch floki foreign-keys hammer headless-browser hmac hooks images javascript keyboard liveview llm markdown mcp media meta mfa migrations monitoring multi-tenancy nimble_publisher nimble_totp oauth2 oban oidc onboarding open-graph passkeys performance philosophy phoenix pkce podcasts postgres postgresql privoxy ranking rate-limiting rss scraping security seo svg syntax-highlighting tor totp upsert ux wax wcag webauthn webhooks xandra
Zero-write upserts in Ecto with IS DISTINCT FROM

A plain ON CONFLICT DO UPDATE writes the row even when nothing changed — every feed poll rewrites thousands of identical entries, bumping updated_at and burning WAL. One SQL clause, IS DISTINCT FROM, makes Postgres skip the no-op write. The catch: when it skips, RETURNING returns nothing and Ecto raises StaleEntryError. Here is the full pattern, the rescue trick that turns the error into an :unchanged result, and the three-layer RSS dedup strategy it sits inside.

elixir ecto postgresql upsert rss performance
Subscribe via RSS