Add 'distance(geometry, geometry)' exrepssion function

CHANGES

@@ -1,6 +1,8 @@
 * Allow argument to muninn.open() to be a direct url or path to a muninn
   configuration file.
 
+* Added 'distance(geometry,geometry)' expression function.
+
 * Fixed issue when pulling a product that is a directory using the S3 remote
   backend.
 

docs/expr.md

@@ -121,6 +121,9 @@ range formed by the second pair of timestamps. Both time ranges are closed.
 The function ``covers(geometry, geometry)`` returns true if the first geometry
 covers the second geometry.
 
+The function ``distance(geometry, geometry)`` returns the distance between
+the two geometries with unit degrees.
+
 The function ``intersects(geometry, geometry)`` returns true if the first
 geometry intersects the second geometry.
 
@@ -148,7 +151,9 @@ UTC.
 
   ``covers(core.validity_start, core.validity_stop, @start, @stop)``
 
-  ``not covers(core.footprint, POINT (5.0 52.0))``
+  ``not covers(core.footprint, POINT(5.0 52.0))``
+
+  ``distance(core.footprint, POINT(5.0 52.0)) < 5``
 
   ``is_derived_from(32a61528-a712-427a-b28f-8ebd5b472b16)``
 

muninn/database/postgresql.py

@@ -596,6 +596,10 @@ def _rewriter_table(self):
         rewriter_table[Prototype("covers", (Geometry, Geometry), Boolean)] = \
             sql.binary_function_rewriter("ST_Covers")
 
+        # use faster non-spheroid distance calculation by passing use_spheroid = false
+        rewriter_table[Prototype("distance", (Geometry, Geometry), Real)] = \
+            lambda arg0, arg1: "ST_Distance(%s, %s, false)" % (arg0, arg1)
+
         rewriter_table[Prototype("intersects", (Geometry, Geometry), Boolean)] = \
             sql.binary_function_rewriter("ST_Intersects")
 

muninn/database/sqlite.py

@@ -528,6 +528,9 @@ def _rewriter_table(self):
         rewriter_table[Prototype("covers", (Geometry, Geometry), Boolean)] = \
             lambda arg0, arg1: "(ST_Covers(%s, %s)=1)" % (arg0, arg1)
 
+        rewriter_table[Prototype("distance", (Geometry, Geometry), Real)] = \
+            lambda arg0, arg1: "ST_Distance(%s, %s)" % (arg0, arg1)
+
         rewriter_table[Prototype("intersects", (Geometry, Geometry), Boolean)] = \
             lambda arg0, arg1: "(ST_Intersects(%s, %s)=1)" % (arg0, arg1)
 

muninn/language.py

@@ -180,6 +180,7 @@
 #
 function_table.add(Prototype("covers", (Geometry, Geometry), Boolean))
 function_table.add(Prototype("covers", (Timestamp, Timestamp, Timestamp, Timestamp), Boolean))
+function_table.add(Prototype("distance", (Geometry, Geometry), Real))
 function_table.add(Prototype("intersects", (Geometry, Geometry), Boolean))
 function_table.add(Prototype("intersects", (Timestamp, Timestamp, Timestamp, Timestamp), Boolean))
 function_table.add(Prototype("is_defined", (Long,), Boolean))