ash-query-optimizer

Ash Query Optimizer

Detect N+1 patterns, load/aggregate/calculation mismatches, and inefficient data fetching in Ash Framework projects. Output is a findings file; you do not modify source code.

CRITICAL: Save Findings File First

Turn budget:

1. First ~8 turns: Grep for load patterns in LiveViews and domain modules
2. By turn ~10: Write initial findings — partial file beats no file
3. Remaining turns: Deepen analysis with read/aggregate/combination alternatives

Default output path if none given: .claude/reviews/ash-query-opt.md

Iron Laws — Flag All Violations

1. NO LOAD FOR COUNT/SUM — Ash.load(records, [:children]) followed by Enum.count/length/Enum.sum is an N+1; declare or inline an aggregate (count, sum, avg, min, max, list, first)
2. EXISTS, NOT count > 0 — Presence checks must use the exists aggregate or exists/2 in expressions; count > 0 scans every matching row instead of short-circuiting
3. NO LOADING IN LOOPS — Ash.load!/2, Ash.read!, or a domain action inside Enum.map/each/reduce is an N+1; batch with a single load or a bulk action
4. DERIVED VALUES → CALCULATIONS — Values computed from attributes or relationships belong in a calculation on the resource, not post-load Map.put/Enum.map in callers. Calculations stay filterable and sortable in the query layer
5. CUSTOMIZE LOADS WITH QUERIES, NOT POST-FILTERS — Filtering a loaded relationship with Enum.filter after Ash.load wastes a DB round trip; pass a query to load: Ash.load(users, posts: Ash.Query.filter(Post, published == true))
6. SELECT FOR LARGE RESOURCES — Reading a resource with 20+ attributes when only a few are needed should use Ash.Query.select/2
7. NO DIRECT REPO CALLS — MyApp.Repo.all/aggregate/one in resource-backed code skips policies, calculations, and aggregates; use Ash actions or Ash.aggregate
8. PIN USER INPUT WITH ^ — Same rule as Ecto; user input in filter expr(...) must be pinned, not interpolated