store: Batch BattingCard/BattingCardRatings lookups in paper-dynasty-database lineup builder

graph/fixes/batch-battingcardbattingcardratings-lookups-in-paper-dynasty-ce86b4.md

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+---
+id: ce86b4d5-0738-46b5-b08c-06d454404a12
+type: fix
+title: "Batch BattingCard/BattingCardRatings lookups in paper-dynasty-database lineup builder"
+tags: [paper-dynasty-database, python, peewee, performance, batch-query, sqlite, fix]
+importance: 0.6
+confidence: 0.8
+created: "2026-03-03T23:35:08.886774+00:00"
+updated: "2026-03-03T23:35:08.886774+00:00"
+---
+
+## Problem
+`get_bratings()` helper inside `build_lineup` endpoint (`app/routers_v2/teams.py`) called `BattingCard.get_or_none` + 2× `BattingCardRatings.get_or_none` per player — O(3N) DB round trips per lineup call.
+
+## Root Cause
+Nested per-player queries inside a Peewee ORM function that was called for each position candidate in the lineup loop.
+
+## Solution
+Before the position loop, batch-fetch all BattingCards and BattingCardRatings for legal_players ∪ backup_players using two bulk SELECTs. Store results in dicts:
+- `_batting_cards_by_player`: `player_id → BattingCard`
+- `_ratings_by_card_hand`: `card_id → {hand → BattingCardRatings}`
+
+Rewrite `get_bratings(player_id)` to do O(1) dict lookups. Error behaviour (AttributeError when card/rating missing) is preserved for existing try/except callers.
+
+## Pattern (reusable)
+```python
+_batch_bcards = BattingCard.select().where(
+    (BattingCard.player << legal_players) | (BattingCard.player << backup_players)
+)
+_batting_cards_by_player = {bc.player_id: bc for bc in _batch_bcards}
+_all_bratings = (
+    BattingCardRatings.select().where(
+        BattingCardRatings.battingcard << list(_batting_cards_by_player.values())
+    )
+    if _batting_cards_by_player else []
+)
+_ratings_by_card_hand = {}
+for _r in _all_bratings:
+    _ratings_by_card_hand.setdefault(_r.battingcard_id, {})[_r.vs_hand] = _r
+```
+
+## Files Changed
+- `app/routers_v2/teams.py` (lines 366–400)
+
+## PR
+https://git.manticorum.com/cal/paper-dynasty-database/pulls/45 (issue #18)