[SCM] PostGIS branch stable-3.6 updated. 3.6.4-61-gae1c72fa7

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- Log -----------------------------------------------------------------
commit ae1c72fa7c510767dff7be53ce0653170b7876a1
Author: Darafei Praliaskouski <me at komzpa.net>
Date:   Sun Nov 30 00:26:34 2025 +0400

    Guard in MakeTopologyPrecise to prevent EMPTY edges
    
    Closes #5948 for PostGIS 3.6.5

diff --git a/NEWS b/NEWS
index 3a478b3bb..0dbd1265e 100644
--- a/NEWS
+++ b/NEWS
@@ -32,6 +32,8 @@ PostGIS 3.6.5
   ring-orientation precision regressions (Darafei Praliaskouski)
 - GH-1146, Reset interrupt callbacks when PostgreSQL clears
   cancellation state (Darafei Praliaskouski)
+- #5948, [topology] Prevent MakeTopologyPrecise from erasing edges when
+          grid size exceeds their extent (Darafei Praliaskouski)
 
 
 PostGIS 3.6.4
diff --git a/doc/extras_topology.xml b/doc/extras_topology.xml
index 833ad2ca1..bdcfe70b4 100644
--- a/doc/extras_topology.xml
+++ b/doc/extras_topology.xml
@@ -1103,6 +1103,13 @@ parameter, optionally limiting the operation to the objects
 intersecting the area specified by the <varname>bbox</varname> parameter.
                 </para>
 
+                <para>
+Using a <varname>gridSize</varname> larger than the smallest edge extent
+raises an exception rather than collapsing the edge into an empty
+geometry. This safeguards adjacent topological relationships by
+preventing precision snapping from removing primitives altogether.
+                </para>
+
 <note>
 <para>
 Snapping could make the topology invalid, so it is recommended to
diff --git a/topology/sql/manage/MakeTopologyPrecise.sql.in b/topology/sql/manage/MakeTopologyPrecise.sql.in
index e66eea2fb..3906e0cfb 100644
--- a/topology/sql/manage/MakeTopologyPrecise.sql.in
+++ b/topology/sql/manage/MakeTopologyPrecise.sql.in
@@ -28,6 +28,7 @@ DECLARE
   dataBox GEOMETRY;
   dataMagnitude FLOAT8;
   minGridSize FLOAT8;
+  minEdgeExtent FLOAT8;
 BEGIN
   topo := findTopology(toponame);
   IF topo.id IS NULL THEN
@@ -73,6 +74,29 @@ BEGIN
   -- TODO: recursively grow working bbox to include all edges connected
   --       to all endpoints of edges intersecting it ?
 
+  --
+  -- Guard against snapping a whole edge to a single grid point.
+  -- With a grid size wider than the smallest edge extent every vertex would
+  -- quantize to the same coordinate, producing EMPTY geometries and breaking
+  -- the topology. Raising early keeps the caller in control of a safer grid
+  -- selection.
+  --
+  sql := format(
+    $$
+SELECT min(greatest(
+    abs(ST_XMax(geom) - ST_XMin(geom)),
+    abs(ST_YMax(geom) - ST_YMin(geom))
+  ))
+FROM %1$I.edge_data
+WHERE ($1 IS NULL OR geom && $1)
+    $$, topo.name
+  );
+  EXECUTE sql USING bbox INTO minEdgeExtent;
+
+  IF minEdgeExtent IS NOT NULL AND gridSize > minEdgeExtent THEN
+    RAISE EXCEPTION 'Grid size % exceeds smallest edge extent % and would erase edges', gridSize, minEdgeExtent;
+  END IF;
+
   sql := format(
     $$
 UPDATE %1$I.edge_data
diff --git a/topology/test/regress/maketopologyprecise.sql b/topology/test/regress/maketopologyprecise.sql
index 84234cd25..f76b535be 100644
--- a/topology/test/regress/maketopologyprecise.sql
+++ b/topology/test/regress/maketopologyprecise.sql
@@ -11,6 +11,12 @@ SELECT 'prec5', 'e', edge_id, ST_AsEWKT(geom) FROM topo.edge ORDER BY edge_id;
 
 SET client_min_messages TO WARNING;
 
+-- A tiny topology exercises the guard against collapsing edges into EMPTY.
+SELECT NULL FROM topology.CreateTopology('tiny');
+SELECT NULL FROM topology.TopoGeo_addLineString('tiny', 'LINESTRING(0 0, 1 0)');
+SELECT topology.MakeTopologyPrecise('tiny', gridSize => 5);
+SELECT NULL FROM topology.DropTopology('tiny');
+
 -- TODO: test bbox limited made-precise topology
 
 -- Cleanup
diff --git a/topology/test/regress/maketopologyprecise_expected b/topology/test/regress/maketopologyprecise_expected
index 2aad628f6..f3e132dad 100644
--- a/topology/test/regress/maketopologyprecise_expected
+++ b/topology/test/regress/maketopologyprecise_expected
@@ -3,3 +3,4 @@ NOTICE:  Every vertex is precise in an empty topology
 ERROR:  Presence of max ordinate value 1002003008 requires a minimum grid size of 3.60721082879999e-6
 start|e|1|LINESTRING(123456789 0.1,6 -1002003004)
 prec5|e|1|LINESTRING(123456790 0,5 -1002003005)
+ERROR:  Grid size 5 exceeds smallest edge extent 1 and would erase edges

-----------------------------------------------------------------------

Summary of changes:
 NEWS                                               |  2 ++
 doc/extras_topology.xml                            |  7 +++++++
 topology/sql/manage/MakeTopologyPrecise.sql.in     | 24 ++++++++++++++++++++++
 topology/test/regress/maketopologyprecise.sql      |  6 ++++++
 topology/test/regress/maketopologyprecise_expected |  1 +
 5 files changed, 40 insertions(+)


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