Add hexagon backend

pipeline/sources/property_prices.py

@@ -0,0 +1,41 @@
+import polars as pl
+
+from pipeline.base import DataSource
+from pipeline.config import DATA_DIR, H3_RESOLUTIONS
+
+
+class PropertyPricesSource(DataSource):
+    """Land Registry property prices data source."""
+
+    @property
+    def name(self) -> str:
+        return "property_prices"
+
+    def load(self) -> pl.LazyFrame:
+        """Load raw property prices data."""
+        return pl.scan_parquet(DATA_DIR / "pp-complete.parquet")
+
+    def process(self, postcodes: pl.LazyFrame) -> pl.LazyFrame:
+        """Process and join with postcode coordinates and H3 indices."""
+        prices = self.load().select(
+            pl.col("price"),
+            pl.col("date_of_transfer").dt.year().alias("year"),
+            pl.col("property_type"),
+            pl.col("postcode"),
+        )
+
+        joined = prices.join(
+            postcodes,
+            on="postcode",
+            how="inner",
+        )
+
+        h3_cols = [pl.col(f"h3_res{res}") for res in H3_RESOLUTIONS]
+        return joined.select(
+            pl.col("price"),
+            pl.col("year"),
+            pl.col("property_type"),
+            pl.col("lat"),
+            pl.col("long"),
+            *h3_cols,
+        )