~/talk

I Didn't Know Querysets Could do That

Talkat DjangoCon US 2016 · 2016-07-17..07-22· [django]

speaker

name:Charlie Guo

links:none on file

resources

video:https://youtu.be/5y7vU52jOiQ

slides:none on file

summary

Shows concrete QuerySet recipes: use F() and Q() to build atomic, single‑SQL operations (e.g. Sum(F('unit_price') F('quantity'), output_field=FloatField()) to compute item totals), use select_related/prefetch_related to eliminate N+1 queries, use in_bulk* to get id→model maps, use only/defer to fetch fewer columns, use ExpressionWrapper and DB functions for inline transforms, and fall back to extra/raw SQL when native expressions can’t express the query. Examples run and avoid Python loops and race conditions.

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