Copilot commented on code in PR #2854:
URL: https://github.com/apache/sedona/pull/2854#discussion_r3125554667
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spark/common/src/main/scala/org/apache/spark/sql/sedona_sql/expressions/Functions.scala:
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@@ -247,7 +247,9 @@ private[apache] case class ST_Expand(inputExpressions:
Seq[Expression])
* @param inputExpressions
*/
private[apache] case class ST_Length(inputExpressions: Seq[Expression])
- extends InferredExpression(Functions.length _) {
+ extends InferredExpression(
+ inferrableFunction1(Functions.length),
+
inferrableFunction1(org.apache.sedona.common.geography.Functions.length)) {
Review Comment:
The Scaladoc for ST_Length still says it returns the length of a Geometry,
but this expression now also dual-dispatches to Geography. Update the comment
to reflect the Geography behavior (geodesic length on WGS84 spheroid, meters)
so Spark SQL users aren’t misled by the inline docs.
##########
spark/common/src/test/scala/org/apache/sedona/sql/geography/GeographyFunctionTest.scala:
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@@ -89,10 +89,26 @@ class GeographyFunctionTest extends TestBaseScala {
}
}
- // ─── Level 2: ST_Distance ──────────────────────────────────────────────
+ // ─── Level 2: ST_Length, ST_Distance ───────────────────────────────────
describe("Level 2: Geodesic metrics") {
Review Comment:
The class-level comment says Level 2 is represented by ST_Distance, but this
test suite now also covers ST_Length. Please update the header comment/docs to
include ST_Length as a Level 2 representative to keep the test documentation
accurate.
##########
docs/api/sql/geography/Geography-Functions/ST_Length.md:
##########
@@ -0,0 +1,44 @@
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied. See the License for the
+ specific language governing permissions and limitations
+ under the License.
+ -->
+
+# ST_Length
+
+Introduction: Returns the geodesic length of a geography object in meters,
calculated on the WGS84 spheroid using GeographicLib. Only linestring and
multilinestring geographies have non-zero length. Returns 0 for points and
polygons.
Review Comment:
The introduction claims only LineString/MultiLineString geographies have
non-zero length, but Geography also supports GEOMETRYCOLLECTION and ST_Length
will return the sum of linear components for collections containing lines.
Update the wording to include geography collections (or clarify that the rule
applies to non-collection types) to avoid incorrect docs.
```suggestion
Introduction: Returns the geodesic length of a geography object in meters,
calculated on the WGS84 spheroid using GeographicLib. Linestring and
multilinestring geographies have non-zero length, and geometrycollection
geographies return the sum of the lengths of their linear components. Returns 0
for points and polygons.
```
##########
common/src/main/java/org/apache/sedona/common/geography/Functions.java:
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@@ -87,6 +88,12 @@ public static int nPoints(Geography g) {
// ─── Level 2: JTS + S2 geodesic metrics ──────────────────────────────────
+ /** Geodesic length in meters (WGS84 spheroid). Returns 0 for non-linear
geographies. */
+ public static double length(Geography g) {
+ if (g == null) return 0.0;
+ return Spheroid.length(toJTS(g));
+ }
Review Comment:
The section header says “JTS + S2 geodesic metrics”, but the new length()
implementation uses the WGS84 spheroid (GeographicLib via Spheroid), not S2.
Consider renaming this section header (or adding a brief note) so it doesn’t
imply ST_Length is S2-based.
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