initial commit

request_coalescing_py/database.py

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+import asyncio
+from typing import Optional
+
+from fastapi import FastAPI
+from databases import Database
+
+from request_coalescing_py.models import Item
+
+
+class DatabaseRepo:
+    def __init__(self, app: FastAPI) -> None:
+        self.app = app
+
+    async def start_db(self) -> None:
+        self._db = Database("sqlite://./test.db")
+        await self._db.connect()
+        
+        try:
+            await self._db.execute(query="CREATE TABLE IF NOT EXISTS 'items' (id INTEGER PRIMARY KEY, name TEXT)")
+            await self._db.execute(query="INSERT INTO 'items' (id, name) VALUES (1, 'Test Item')")
+        except Exception:
+            pass
+
+    async def stop_db(self) -> None:
+        await self._db.disconnect()
+
+    async def get_by_id(self, item_id: int) -> Optional[Item]:
+        self.app.state.metrics["db_calls"] += 1
+
+        # Simulate expensive read (50ms)
+        await asyncio.sleep(.05)
+
+        row = await self._db.fetch_one(query="SELECT * FROM 'items' WHERE id = :id", values={"id": item_id})
+        if row:
+            return Item(**row._mapping)
+        
+        return None