_fetch_anchor_comps Tier A runs on EVERY /estimate (flag
estimate_same_building_anchor_enabled defaults True, not overridden in prod).
Its address predicate wraps address in lower(translate(address,'ёЁ','ее')) for
both the LIKE '%street%' and the ~house-number regex — non-sargable, and the
existing listings_address_trgm_idx is on the RAW address, so the planner
seq-scanned all ~66.7k listings (167ms, 15801 buffers) every estimate.
Add a GIN trigram expression index on lower(translate(address,'ёЁ','ее'))
matching the predicate exactly (gin_trgm_ops serves both LIKE and the regex).
Prod EXPLAIN (BEGIN/ROLLBACK, "Хохрякова 48"): 167ms -> 1.77ms (~94x), buffers
15801 -> 97. Independently dry-run-verified: Bitmap Index Scan, 0.66ms.
Result-identical (pure access-path; count/sum/min/max unchanged). No code
change (expression matches the predicate). ~8MB, sub-second build.
Other estimate-path queries confirmed already optimal (Tier W/H geom+rooms
BitmapAnd, Tier S house_id_fk) — no other index warranted.
tradein-mvp/backend/data/sql/137 (correct tradein migrations path).
