fix: add transaction safety and type validation to PriceCollector

- Implement per-ticker commits to ensure atomic operations per data source
- Add rollback on exception to prevent partial data corruption
- Add _safe_float() and _safe_int() helper methods for defensive type conversion
- Validate column count after DataFrame reset to catch schema issues early
- Skip records with missing essential values (close price) with debug logging
- Remove final db.commit() since commits now happen per ticker in the loop

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/collectors/price_collector.py

@@ -36,6 +36,24 @@ class PriceCollector(BaseCollector):
             except ValueError:
                 raise ValueError(f"Invalid {name} format. Expected YYYYMMDD, got: {date_str}")
 
+    def _safe_float(self, value) -> float | None:
+        """Safely convert value to float."""
+        if pd.isna(value):
+            return None
+        try:
+            return float(value)
+        except (ValueError, TypeError):
+            return None
+
+    def _safe_int(self, value) -> int | None:
+        """Safely convert value to int."""
+        if pd.isna(value):
+            return None
+        try:
+            return int(float(value))
+        except (ValueError, TypeError):
+            return None
+
     def collect(self) -> int:
         """Collect price data for all stocks."""
         # Get list of tickers from database
@@ -62,16 +80,35 @@ class PriceCollector(BaseCollector):
                 df.columns = ["date", "open", "high", "low", "close", "volume",
                              "value", "change"]
 
+                # Validate column count
+                expected_cols = 8  # date + 7 data columns
+                if len(df.columns) < expected_cols:
+                    logger.warning(f"Unexpected column count for {ticker}: {len(df.columns)}")
+                    continue
+
                 records = []
                 for _, row in df.iterrows():
+                    # Safely convert values with type checking
+                    open_val = self._safe_float(row["open"])
+                    high_val = self._safe_float(row["high"])
+                    low_val = self._safe_float(row["low"])
+                    close_val = self._safe_float(row["close"])
+                    volume_val = self._safe_int(row["volume"])
+
+                    # Skip if essential values are missing
+                    if close_val is None:
+                        logger.debug(f"Skipping record for {ticker}: missing close price")
+                        continue
+
+                    date_value = row["date"].date() if hasattr(row["date"], "date") else row["date"]
                     records.append({
                         "ticker": ticker,
-                        "date": row["date"].date() if hasattr(row["date"], "date") else row["date"],
-                        "open": float(row["open"]),
-                        "high": float(row["high"]),
-                        "low": float(row["low"]),
-                        "close": float(row["close"]),
-                        "volume": int(row["volume"]),
+                        "date": date_value,
+                        "open": open_val,
+                        "high": high_val,
+                        "low": low_val,
+                        "close": close_val,
+                        "volume": volume_val,
                     })
 
                 if records:
@@ -87,12 +124,13 @@ class PriceCollector(BaseCollector):
                         },
                     )
                     self.db.execute(stmt)
+                    self.db.commit()  # Commit per ticker
                     total_records += len(records)
 
             except Exception as e:
+                self.db.rollback()  # Rollback on failure
                 logger.warning(f"Failed to fetch prices for {ticker}: {e}")
                 continue
 
-        self.db.commit()
         logger.info(f"Collected {total_records} price records")
         return total_records