feat(sql): Implement ST_StartPoint() and ST_EndPoint() #245

yutannihilation · 2025-10-26T14:55:30Z

As many people are adding geos-related functions, I pick this to avoid collision.

At first, I thought this can be implemented via geo_traits::CoordTrait. But, I read the implementation of ST_Point and felt it's preferable to handle the raw bytes of WKB for performance. While I'm not good at performance, I'm trying to implement it.

The remaining tasks are:

Add Python tests
Add benchmark

paleolimbot · 2025-10-27T01:15:59Z

As many people are adding geos-related functions, I pick this to avoid collision.

Thank you!

At first, I thought this can be implemented via geo_traits::CoordTrait. But, I read the implementation of ST_Point and felt it's preferable to handle the raw bytes of WKB for performance.

I think using GeoTraits or the Wkb object directly would be roughly equivalent in terms of performance and would be a whole lot easier to write. While we do care about performance, we also care about bug surface area and maintainability. There are some functions were we work with WKB bytes directly but all of them had simpler implementations first that we benchmarked to ensure that the complexity had measurable benefit.

yutannihilation · 2025-10-27T15:20:29Z

Thanks for the hint! Now I figured out how to do it with geo-traits and the functions in wkb_factory.rs.

yutannihilation · 2025-10-27T16:03:50Z

It seems I still have troubles on running Python tests on my Windows, so I don't run these Python tests yet. I'll try on macOS tomorrow. Anyway, I believe this pull request is ready for review now.

paleolimbot

Just a few things to consider...thank you!

I'll try to work on the Windows development situation soon 😬

python/sedonadb/tests/functions/test_functions.py

rust/sedona-functions/src/st_start_point.rs

paleolimbot · 2025-10-28T04:22:09Z

rust/sedona-functions/src/st_start_point.rs

+    match dim.size() {
+        2 => {
+            let coords_tuple = coords.x_y();
+            write_wkb_coord(buf, coords_tuple)
+        }
+        3 => {
+            let coords_tuple = (coords.x(), coords.y(), coords.nth_or_panic(2));
+            write_wkb_coord(buf, coords_tuple)
+        }
+        4 => {
+            let coords_tuple = (
+                coords.x(),
+                coords.y(),
+                coords.nth_or_panic(2),
+                coords.nth_or_panic(3),
+            );
+            write_wkb_coord(buf, coords_tuple)
+        }
+        _ => Err(SedonaGeometryError::Invalid(
+            "Unsupported number of dimensions".to_string(),
+        )),
+    }


This would fit nicely as wkb_factory::write_wkb_coord_trait() (I'm sure we'll need it again!)

Thanks, moved the implementation to wkb_factory now.

Co-authored-by: Dewey Dunnington <[email protected]>

yutannihilation · 2025-10-28T11:04:32Z

Thanks for reviewing!

Sorry, this was unexpected, but I just found the document has this small note

Enhanced: 3.2.0 returns a point for all geometries. Prior behavior returns NULLs if input was not a LineString.

and this is the actual behavior (while the example on the document returns t...)

postgres=# SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
 is_null 
---------
 f
(1 row)

Probably I need some time to update the implementation.

yutannihilation · 2025-10-28T12:58:07Z

I think this should be ready for review again now!

Benchmark result:

--------------------------------------------------------------------------------------------------------- benchmark: 6 tests --------------------------------------------------------------------------------------------------------
Name (time in ms)                                                     Min                 Max                Mean            StdDev              Median               IQR            Outliers       OPS            Rounds  Iterations
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_st_start_point[segments_large-SedonaDBSingleThread]           1.9418 (1.0)        2.3150 (1.0)        2.0126 (1.0)      0.0812 (1.0)        1.9881 (1.0)      0.0475 (1.0)           2;2  496.8624 (1.0)          26           1
test_st_start_point[collections_simple-DuckDBSingleThread]         6.3318 (3.26)       7.5675 (3.27)       6.7992 (3.38)     0.4783 (5.89)       6.6988 (3.37)     0.6017 (12.66)         1;0  147.0758 (0.30)          5           1
test_st_start_point[segments_large-DuckDBSingleThread]             7.6638 (3.95)       8.6637 (3.74)       7.9898 (3.97)     0.3350 (4.12)       7.8963 (3.97)     0.2996 (6.30)          1;1  125.1591 (0.25)          7           1
test_st_start_point[collections_simple-SedonaDBSingleThread]      10.4538 (5.38)      11.3186 (4.89)      10.6016 (5.27)     0.2383 (2.93)      10.5149 (5.29)     0.0893 (1.88)          2;3   94.3255 (0.19)         20           1
test_st_start_point[segments_large-PostGISSingleThread]          240.1957 (123.70)   243.3285 (105.11)   241.3920 (119.94)   1.1893 (14.64)    241.1900 (121.32)   1.3549 (28.50)         2;0    4.1426 (0.01)          5           1
test_st_start_point[collections_simple-PostGISSingleThread]      352.2113 (181.39)   357.8562 (154.58)   355.9990 (176.88)   2.3396 (28.80)    357.1065 (179.63)   3.0995 (65.20)         1;0    2.8090 (0.01)          5           1
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Legend:
  Outliers: 1 Standard Deviation from Mean; 1.5 IQR (InterQuartile Range) from 1st Quartile and 3rd Quartile.
  OPS: Operations Per Second, computed as 1 / Mean

martin-g · 2025-10-28T15:57:18Z

rust/sedona-functions/src/st_start_point.rs

+fn st_start_point_doc() -> Documentation {
+    Documentation::builder(
+        DOC_SECTION_OTHER,
+        "Returns the start point of a LINESTRING geometry. Returns NULL if the geometry is not a LINESTRING.",


According to https://github.com/apache/sedona-db/pull/245/files#diff-6675d3a4b31524e6b409c5e557bdecd20adb0615fba805d77ba4b52a61c4dae5R142-R143 this is correct for the end point, not for the start one.

paleolimbot

It would be good to take care of the documentation and test suggestions here but I this is a great implementation and we can also handle that in a follow-on ticket if needed. Thank you!

python/sedonadb/tests/functions/test_functions.py

paleolimbot · 2025-10-28T17:47:03Z

python/sedonadb/tests/functions/test_functions.py

+    [
+        ("LINESTRING (1 2, 3 4, 5 6)", "POINT (5 6)"),


NULL and empties would be good to test here, too.

rust/sedona-functions/src/st_start_point.rs

paleolimbot · 2025-10-28T17:57:57Z

rust/sedona-functions/src/st_start_point.rs

+        let input = create_array(
+            &[
+                Some("LINESTRING (1 2, 3 4, 5 6)"),


For full test coverage of your implementation I think we would need to test empty geometries here as well.

Co-authored-by: Dewey Dunnington <[email protected]>

yutannihilation · 2025-10-28T22:03:05Z

Thanks for the great review! Adding tests about empty geometry actually helped me to find a bug in my implementation of ST_EndPoint :) I think I addressed all the comments now.

paleolimbot

Thank you!

feat(sql): Implement ST_StartPoint() and ST_EndPoint()

1c59285

Use geo-traits

1e50ef0

yutannihilation added 3 commits October 28, 2025 00:57

Add Python tests

2024c21

Use geom_or_null

9e246ac

Add benchmarks

00b4191

yutannihilation marked this pull request as ready for review October 27, 2025 16:01

paleolimbot reviewed Oct 28, 2025

View reviewed changes

yutannihilation and others added 2 commits October 28, 2025 19:20

Apply suggestions from code review

a6cc101

Co-authored-by: Dewey Dunnington <[email protected]>

Fix function name

96f9232

yutannihilation added 3 commits October 28, 2025 20:34

Add write_wkb_coord_trait

0368d9b

Handle other geometries

192e185

Add Python benchmark

e67cd35

martin-g reviewed Oct 28, 2025

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paleolimbot approved these changes Oct 28, 2025

View reviewed changes

yutannihilation and others added 2 commits October 29, 2025 06:51

Apply suggestions from code review

be03b48

Co-authored-by: Dewey Dunnington <[email protected]>

Address comments and fix a bug

fecb158

paleolimbot approved these changes Oct 29, 2025

View reviewed changes

paleolimbot merged commit 0551583 into apache:main Oct 29, 2025
12 checks passed

yutannihilation deleted the feat/st_start_point branch October 29, 2025 03:37

feat(sql): Implement ST_StartPoint() and ST_EndPoint() #245

feat(sql): Implement ST_StartPoint() and ST_EndPoint() #245

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