Added the EmptySearch class (#1780)

(cherry picked from commit 6cfbbe1)

Author: miguelgrinberg

docs/search_dsl.rst

@@ -666,3 +666,10 @@ If you need to execute multiple searches at the same time you can use the
         print("Results for query %r." % response.search.query)
         for hit in response:
             print(hit.title)
+
+
+``EmptySearch``
+---------------
+
+The ``EmptySearch`` class can be used as a fully compatible version of ``Search``
+that will return no results, regardless of any queries configured.

elasticsearch_dsl/__init__.py

@@ -81,7 +81,14 @@
 from .index import AsyncIndex, AsyncIndexTemplate, Index, IndexTemplate
 from .mapping import AsyncMapping, Mapping
 from .query import Q
-from .search import AsyncMultiSearch, AsyncSearch, MultiSearch, Search
+from .search import (
+    AsyncEmptySearch,
+    AsyncMultiSearch,
+    AsyncSearch,
+    EmptySearch,
+    MultiSearch,
+    Search,
+)
 from .update_by_query import AsyncUpdateByQuery, UpdateByQuery
 from .utils import AttrDict, AttrList, DslBase
 from .wrappers import Range
@@ -92,6 +99,7 @@
 __all__ = [
     "A",
     "AsyncDocument",
+    "AsyncEmptySearch",
     "AsyncFacetedSearch",
     "AsyncIndex",
     "AsyncIndexTemplate",
@@ -115,6 +123,7 @@
     "DoubleRange",
     "DslBase",
     "ElasticsearchDslException",
+    "EmptySearch",
     "Facet",
     "FacetedResponse",
     "FacetedSearch",

elasticsearch_dsl/_async/search.py

@@ -144,3 +144,18 @@ async def execute(self, ignore_cache=False, raise_on_error=True):
             self._response = out
 
         return self._response
+
+
+class AsyncEmptySearch(AsyncSearch):
+    async def count(self):
+        return 0
+
+    async def execute(self, ignore_cache=False):
+        return self._response_class(self, {"hits": {"total": 0, "hits": []}})
+
+    async def scan(self):
+        return
+        yield  # a bit strange, but this forces an empty generator function
+
+    async def delete(self):
+        return AttrDict({})

elasticsearch_dsl/_sync/search.py

@@ -136,3 +136,18 @@ def execute(self, ignore_cache=False, raise_on_error=True):
             self._response = out
 
         return self._response
+
+
+class EmptySearch(Search):
+    def count(self):
+        return 0
+
+    def execute(self, ignore_cache=False):
+        return self._response_class(self, {"hits": {"total": 0, "hits": []}})
+
+    def scan(self):
+        return
+        yield  # a bit strange, but this forces an empty generator function
+
+    def delete(self):
+        return AttrDict({})

elasticsearch_dsl/search.py

@@ -15,6 +15,14 @@
 #  specific language governing permissions and limitations
 #  under the License.
 
-from elasticsearch_dsl._async.search import AsyncMultiSearch, AsyncSearch  # noqa: F401
-from elasticsearch_dsl._sync.search import MultiSearch, Search  # noqa: F401
+from elasticsearch_dsl._async.search import (  # noqa: F401
+    AsyncEmptySearch,
+    AsyncMultiSearch,
+    AsyncSearch,
+)
+from elasticsearch_dsl._sync.search import (  # noqa: F401
+    EmptySearch,
+    MultiSearch,
+    Search,
+)
 from elasticsearch_dsl.search_base import Q  # noqa: F401

tests/_async/test_search.py

@@ -19,7 +19,7 @@
 
 from pytest import raises
 
-from elasticsearch_dsl import AsyncSearch, Document, Q, query
+from elasticsearch_dsl import A, AsyncEmptySearch, AsyncSearch, Document, Q, query
 from elasticsearch_dsl.exceptions import IllegalOperation
 
 
@@ -681,3 +681,14 @@ def test_rescore_query_to_dict():
             },
         },
     }
+
+
+async def test_empty_search():
+    s = AsyncEmptySearch(index="index-name")
+    s = s.query("match", lang="java")
+    s.aggs.bucket("versions", A("terms", field="version"))
+
+    assert await s.count() == 0
+    assert [hit async for hit in s] == []
+    assert [hit async for hit in s.scan()] == []
+    await s.delete()  # should not error

tests/_sync/test_search.py

@@ -19,7 +19,7 @@
 
 from pytest import raises
 
-from elasticsearch_dsl import Document, Q, Search, query
+from elasticsearch_dsl import A, Document, EmptySearch, Q, Search, query
 from elasticsearch_dsl.exceptions import IllegalOperation
 
 
@@ -679,3 +679,14 @@ def test_rescore_query_to_dict():
             },
         },
     }
+
+
+def test_empty_search():
+    s = EmptySearch(index="index-name")
+    s = s.query("match", lang="java")
+    s.aggs.bucket("versions", A("terms", field="version"))
+
+    assert s.count() == 0
+    assert [hit for hit in s] == []
+    assert [hit for hit in s.scan()] == []
+    s.delete()  # should not error

utils/run-unasync.py

@@ -52,6 +52,7 @@ def main(check=False):
         "AsyncElasticsearch": "Elasticsearch",
         "AsyncSearch": "Search",
         "AsyncMultiSearch": "MultiSearch",
+        "AsyncEmptySearch": "EmptySearch",
         "AsyncDocument": "Document",
         "AsyncIndexMeta": "IndexMeta",
         "AsyncIndexTemplate": "IndexTemplate",