feat: TTL purge — purge_old_sessions + /purge command + startup hook

src/db/database.py

@@ -5,8 +5,12 @@ from pathlib import Path
 from typing import Optional
 from enum import Enum
 
+import structlog
+
 from src.config import settings
 
+logger = structlog.get_logger()
+
 
 class ResearchStatus(str, Enum):
     RUNNING = "running"
@@ -266,3 +270,36 @@ class ResearchDB:
         )
         rows = await cursor.fetchall()
         return [dict(r) for r in rows]
+
+    # --- Maintenance ---
+
+    async def purge_old_sessions(self, max_age_days: int = 30) -> dict:
+        await self.db.execute("PRAGMA foreign_keys = ON")
+
+        threshold = time.time() - max_age_days * 86400
+        cursor = await self.db.execute(
+            "SELECT id FROM research_sessions WHERE created_at < ? AND status != 'running'",
+            (threshold,)
+        )
+        session_ids = [row[0] for row in await cursor.fetchall()]
+
+        counts = {"sessions": 0, "sources": 0, "chunks": 0, "outputs": 0}
+
+        for sid in session_ids:
+            await self.db.execute(
+                "DELETE FROM source_contents WHERE source_id IN (SELECT id FROM sources WHERE session_id = ?)",
+                (sid,)
+            )
+            cur = await self.db.execute("DELETE FROM chunks WHERE session_id = ?", (sid,))
+            counts["chunks"] += cur.rowcount
+            cur = await self.db.execute("DELETE FROM outputs WHERE session_id = ?", (sid,))
+            counts["outputs"] += cur.rowcount
+            cur = await self.db.execute("DELETE FROM sources WHERE session_id = ?", (sid,))
+            counts["sources"] += cur.rowcount
+            cur = await self.db.execute("DELETE FROM research_sessions WHERE id = ?", (sid,))
+            counts["sessions"] += cur.rowcount
+
+        await self.db.commit()
+        logger.info("Purged sessions older than days",
+                    sessions=counts["sessions"], days=max_age_days)
+        return counts