[GH-2768] Replace len(self)==0 with cheaper _is_empty() check in GeoSeries (#2770)

Author: jiayuasu

python/sedona/spark/geopandas/geoseries.py

@@ -341,6 +341,10 @@ def __init__(
         if crs:
             self.set_crs(crs, inplace=True)
 
+    def _is_empty(self) -> bool:
+        """Check if this GeoSeries has no rows without triggering a full Spark scan."""
+        return not self._internal.spark_frame.take(1)
+
     # ============================================================================
     # COORDINATE REFERENCE SYSTEM (CRS) OPERATIONS
     # ============================================================================
@@ -382,7 +386,7 @@ def crs(self) -> Union["CRS", None]:
         """
         from pyproj import CRS
 
-        if len(self) == 0:
+        if self._is_empty():
             return None
 
         # F.first is non-deterministic, but it doesn't matter because all non-null values should be the same.
@@ -1152,8 +1156,8 @@ def line_merge(self, directed=False):
         )
 
     def build_area(self, node=True):
-        if len(self) == 0:
-            return GeoSeries([], name="polygons", crs=self.crs)
+        if self._is_empty():
+            return GeoSeries([], name="polygons", crs=None)
 
         if node:
             aggr_expr = sta.ST_Union_Aggr(self.spark.column)
@@ -1189,8 +1193,8 @@ def polygonize(self, node=True, full=False):
                 "Sedona does not support full=True for polygonize."
             )
 
-        if len(self) == 0:
-            return GeoSeries([], name="polygons", crs=self.crs)
+        if self._is_empty():
+            return GeoSeries([], name="polygons", crs=None)
 
         if node:
             aggr_expr = sta.ST_Union_Aggr(self.spark.column)
@@ -1245,7 +1249,7 @@ def union_all(self, method="unary", grid_size=None) -> BaseGeometry:
                 f"Sedona does not support manually specifying different union methods. Ignoring non-default method argument of {method}"
             )
 
-        if len(self) == 0:
+        if self._is_empty():
             # While it's not explicitly defined in GeoPandas docs, this is what GeoPandas returns for empty GeoSeries.
             # If it ever changes for some reason, we'll catch that with the test
             from shapely.geometry import GeometryCollection
@@ -1260,7 +1264,7 @@ def union_all(self, method="unary", grid_size=None) -> BaseGeometry:
         return geom
 
     def intersection_all(self) -> BaseGeometry:
-        if len(self) == 0:
+        if self._is_empty():
             from shapely.geometry import GeometryCollection
 
             return GeometryCollection()
@@ -2645,7 +2649,7 @@ def bounds(self) -> pspd.DataFrame:
     def total_bounds(self):
         import warnings
 
-        if len(self) == 0:
+        if self._is_empty():
             # numpy 'min' cannot handle empty arrays
             # TODO with numpy >= 1.15, the 'initial' argument can be used
             return np.array([np.nan, np.nan, np.nan, np.nan])