Speed up property function

abcd/backends/atoms_opensearch.py

@@ -9,7 +9,7 @@
 
 from ase import Atoms
 from ase.io import iread
-from opensearchpy import OpenSearch, helpers, AuthenticationException, ConnectionTimeout
+from opensearchpy import OpenSearch, helpers, AuthenticationException, ConnectionTimeout, RequestError
 
 from abcd.backends import utils
 from abcd.database import AbstractABCD
@@ -533,8 +533,7 @@ def count(self, query: Union[dict, str, None] = None) -> int:
     def property(self, name, query: Union[dict, str, None] = None) -> list:
         """
         Gets all values of a specified property for matching documents in the
-        database. This method is very slow, so it is preferable to use
-        alternative methods where possible, such as count_property.
+        database. Alternative methods, such as count_property, may be faster.
 
         Parameters
         ----------
@@ -543,24 +542,39 @@ def property(self, name, query: Union[dict, str, None] = None) -> list:
 
         Returns
         -------
-        List of values for the specified property for all matching documents.
+        list
+            List of values for the specified property for all matching documents.
         """
         query = self.parser(query)
         query = {
             "query": query,
         }
 
-        return [
-            hit["_source"][format(name)]
-            for hit in helpers.scan(
-                self.client,
-                index=self.index_name,
-                query=query,
-                stored_fields=format(name),
-                _source=format(name),
-            )
-            if format(name) in hit["_source"]
-        ]
+        try:
+            return [
+                hit["fields"][format(name)][0]
+                for hit in helpers.scan(
+                    self.client,
+                    index=self.index_name,
+                    query=query,
+                    _source=False,
+                    stored_fields="_none_",
+                    docvalue_fields=[format(name)],
+                )
+                if "fields" in hit and format(name) in hit["fields"]
+            ]
+        except RequestError:
+            return [
+                hit["_source"][format(name)]
+                for hit in helpers.scan(
+                    self.client,
+                    index=self.index_name,
+                    query=query,
+                    stored_fields=format(name),
+                    _source=format(name),
+                )
+                if format(name) in hit["_source"]
+            ]
 
     def count_property(self, name, query: Union[dict, str, None] = None) -> dict:
         """

tests/opensearch.py

@@ -235,7 +235,7 @@ def test_property(self):
 
         xyz_1 = StringIO(
             """2
-            Properties=species:S:1:pos:R:3 s="sadf" prop_1="test_1" pbc="F F F"
+            Properties=species:S:1:pos:R:3 energy=-5.0 prop_1="test_1"
             Si       0.00000000       0.00000000       0.00000000
             Si       0.00000000       0.00000000       0.00000000
             """
@@ -248,7 +248,7 @@ def test_property(self):
 
         xyz_2 = StringIO(
             """2
-            Properties=species:S:1:pos:R:3 s="sadf" prop_2="test_2" pbc="F F F"
+            Properties=species:S:1:pos:R:3 energy=-10.0 prop_2="test_2"
             Si       0.00000000       0.00000000       0.00000000
             Si       0.00000000       0.00000000       0.00000000
             """
@@ -264,6 +264,11 @@ def test_property(self):
         expected_prop = ["test_1"]
         self.assertEqual(prop, expected_prop)
 
+        prop = self.abcd.property("energy")
+        expected_prop = [-5.0, -10.0]
+        self.assertEqual(prop[0], expected_prop[0])
+        self.assertEqual(prop[1], expected_prop[1])
+
     def test_properties(self):
         """
         Test getting all properties from the database.