From c5b66779ed289d0bfc671ca4b918c3a39ece45ed Mon Sep 17 00:00:00 2001
From: Andy Yang <ayang@cockroachlabs.com>
Date: Tue, 23 Mar 2021 23:06:18 -0400
Subject: [PATCH] geo/geomfn: fix st_linelocatepoint to work with ZM coords

Previously, st_linelocatepoint would panic when the
line had Z and/or M coordinates.

Release note: None
---
 pkg/geo/geomfn/linestring.go      | 3 ++-
 pkg/geo/geomfn/linestring_test.go | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/pkg/geo/geomfn/linestring.go b/pkg/geo/geomfn/linestring.go
index 526ca72ec9d3..dc4b35a37b64 100644
--- a/pkg/geo/geomfn/linestring.go
+++ b/pkg/geo/geomfn/linestring.go
@@ -95,8 +95,9 @@ func LineLocatePoint(line geo.Geometry, point geo.Geometry) (float64, error) {
 		return 0, err
 	}
 
+	lineStart := geom.Coord{lineString.Coord(0).X(), lineString.Coord(0).Y()}
 	// build new line segment to the closest point we found
-	lineSegment := geom.NewLineString(geom.XY).MustSetCoords([]geom.Coord{lineString.Coord(0), p.Coords()})
+	lineSegment := geom.NewLineString(geom.XY).MustSetCoords([]geom.Coord{lineStart, p.Coords()})
 
 	// compute fraction of new line segment compared to total line length
 	return lineSegment.Length() / lineString.Length(), nil
diff --git a/pkg/geo/geomfn/linestring_test.go b/pkg/geo/geomfn/linestring_test.go
index b6e7aa9d4a04..f0b15dfa61b7 100644
--- a/pkg/geo/geomfn/linestring_test.go
+++ b/pkg/geo/geomfn/linestring_test.go
@@ -168,6 +168,11 @@ func TestLineLocatePoint(t *testing.T) {
 			point:      geom.NewPointFlat(geom.XY, []float64{3, 1}),
 			expected:   0.87,
 		},
+		{
+			lineString: geom.NewLineStringFlat(geom.XYZ, []float64{0, 0, 5, 1, 1, 26}),
+			point:      geom.NewPointFlat(geom.XYZ, []float64{0, 1, -1}),
+			expected:   0.5,
+		},
 	}
 
 	for index, tc := range testCases {