Add Parquet measurement storage

src/py_dvt_ate/data/repository.py

@@ -1,4 +1,4 @@
-"""Data repository implementation using SQLite.
+"""Data repository implementation using SQLite and Parquet.
 
 This module provides SQLite-based storage for test run metadata and results.
 Time-series measurements are stored separately in Parquet files.
@@ -12,6 +12,8 @@ from pathlib import Path
 from typing import Any
 from uuid import UUID, uuid4
 
+import pandas as pd
+
 from py_dvt_ate.data.models import Measurement, TestResult, TestRun, TestStatus
 
 
@@ -65,25 +67,34 @@ class ITestRepository(ABC):
         """Retrieve all test results for a run."""
 
     @abstractmethod
-    def get_measurements_dataframe(self, run_id: UUID) -> Any:
+    def get_measurements_dataframe(self, run_id: UUID) -> pd.DataFrame | None:
-        """Retrieve measurements as pandas DataFrame (implemented in Parquet extension)."""
+        """Retrieve measurements as pandas DataFrame."""
 
 
 class SQLiteRepository(ITestRepository):
     """SQLite-based repository for test data.
 
     Stores test run metadata and scalar results in SQLite.
-    Time-series measurements are delegated to Parquet files.
+    Time-series measurements are stored in Parquet files.
     """
 
-    def __init__(self, db_path: str | Path):
+    def __init__(self, db_path: str | Path, measurements_dir: str | Path | None = None):
-        """Initialise repository with database path.
+        """Initialise repository with database and measurements paths.
 
         Args:
             db_path: Path to SQLite database file
+            measurements_dir: Directory for Parquet measurement files
+                            (defaults to db_path parent / "measurements")
         """
         self.db_path = Path(db_path)
         self.db_path.parent.mkdir(parents=True, exist_ok=True)
+
+        if measurements_dir is None:
+            self.measurements_dir = self.db_path.parent / "measurements"
+        else:
+            self.measurements_dir = Path(measurements_dir)
+
+        self.measurements_dir.mkdir(parents=True, exist_ok=True)
         self._init_database()
 
     def _init_database(self) -> None:
@@ -243,11 +254,38 @@ class SQLiteRepository(ITestRepository):
         run_id: UUID,
         measurements: list[Measurement],
     ) -> None:
-        """Save time-series measurements.
+        """Save time-series measurements to Parquet file.
 
-        This is a stub - actual implementation will be in Parquet extension (Task 13.3).
+        Measurements are stored in Parquet format for efficient time-series storage.
+        File path: {measurements_dir}/run_{run_id}/measurements.parquet
         """
-        # Will be implemented in Task 13.3 with Parquet support
+        if not measurements:
+            return
+
+        # Create run-specific directory
+        run_dir = self.measurements_dir / f"run_{run_id}"
+        run_dir.mkdir(parents=True, exist_ok=True)
+
+        # Convert measurements to DataFrame
+        data = {
+            "timestamp": [m.timestamp for m in measurements],
+            "parameter": [m.parameter for m in measurements],
+            "value": [m.value for m in measurements],
+            "unit": [m.unit for m in measurements],
+            "temperature": [m.temperature for m in measurements],
+            "input_voltage": [m.input_voltage for m in measurements],
+            "load_current": [m.load_current for m in measurements],
+        }
+        df = pd.DataFrame(data)
+
+        # Save to Parquet (append mode if file exists)
+        parquet_path = run_dir / "measurements.parquet"
+        if parquet_path.exists():
+            # Read existing data and append
+            existing_df = pd.read_parquet(parquet_path)
+            df = pd.concat([existing_df, df], ignore_index=True)
+
+        df.to_parquet(parquet_path, index=False, engine="pyarrow")
 
     def get_run(self, run_id: UUID) -> TestRun:
         """Retrieve test run metadata by ID."""
@@ -304,10 +342,18 @@ class SQLiteRepository(ITestRepository):
                 for row in rows
             ]
 
-    def get_measurements_dataframe(self, run_id: UUID) -> Any:
+    def get_measurements_dataframe(self, run_id: UUID) -> pd.DataFrame | None:
-        """Retrieve measurements as pandas DataFrame.
+        """Retrieve measurements as pandas DataFrame from Parquet file.
 
-        This is a stub - actual implementation will be in Parquet extension (Task 13.3).
+        Args:
+            run_id: Test run ID
+
+        Returns:
+            DataFrame with measurement data, or None if no measurements exist
         """
-        # Will be implemented in Task 13.3 with Parquet support
+        parquet_path = self.measurements_dir / f"run_{run_id}" / "measurements.parquet"
+
+        if not parquet_path.exists():
             return None
+
+        return pd.read_parquet(parquet_path)