Added point in time support and the Search.iterate() method

Author: miguelgrinberg

elasticsearch_dsl/_async/search.py

@@ -15,6 +15,8 @@
 #  specific language governing permissions and limitations
 #  under the License.
 
+import contextlib
+
 from elasticsearch.exceptions import ApiError
 from elasticsearch.helpers import async_scan
 
@@ -92,6 +94,8 @@ async def scan(self):
         pass to the underlying ``scan`` helper from ``elasticsearch-py`` -
         https://elasticsearch-py.readthedocs.io/en/master/helpers.html#elasticsearch.helpers.scan
 
+        The ``iterate()`` method should be preferred, as it provides similar
+        functionality using a point in time.
         """
         es = get_connection(self._using)
 
@@ -113,6 +117,56 @@ async def delete(self):
             )
         )
 
+    @contextlib.asynccontextmanager
+    async def point_in_time(self, keep_alive="1m"):
+        """
+        Open a point in time (pit) that can be used across several searches.
+
+        :arg keep_alive: the time to live for the point in time, renewed with each new search request
+
+        This method implements a context manager that returns a search object
+        configured to operate within the created pit. The following example
+        shows how to paginate through all the documents of an index::
+
+            page_size = 10
+            with Search(index="my-index")[:page_size].point_in_time() as s:
+                while True:
+                    r = s.execute()  # get a page of results
+                    // ... do something with r.hits
+
+                    if len(r.hits) < page_size:
+                        break  # we reached the end
+                    s = r.search_after()
+        """
+        es = get_connection(self._using)
+
+        pit = await es.open_point_in_time(
+            index=self._index or "*", keep_alive=keep_alive
+        )
+        search = self.index().extra(pit={"id": pit["id"], "keep_alive": keep_alive})
+        if not search._sort:
+            search = search.sort("_shard_doc")
+        yield search
+        await es.close_point_in_time(id=pit["id"])
+
+    async def iterate(self, keep_alive="1m"):
+        """
+        Return a generator that iterates over all the documents matching the query.
+
+        :arg keep_alive: the time to live for the point in time, renewed with each new search request
+
+        This method uses a point in time to provide consistent results even when
+        the underlying index is changing. It should be preferred over ``scan()``.
+        """
+        async with self.point_in_time(keep_alive=keep_alive) as s:
+            while True:
+                r = await s.execute()
+                for hit in r:
+                    yield hit
+                if len(r.hits) == 0:
+                    break
+                s = r.search_after()
+
 
 class AsyncMultiSearch(MultiSearchBase):
     """

elasticsearch_dsl/_sync/search.py

@@ -15,6 +15,8 @@
 #  specific language governing permissions and limitations
 #  under the License.
 
+import contextlib
+
 from elasticsearch.exceptions import ApiError
 from elasticsearch.helpers import scan
 
@@ -88,6 +90,8 @@ def scan(self):
         pass to the underlying ``scan`` helper from ``elasticsearch-py`` -
         https://elasticsearch-py.readthedocs.io/en/master/helpers.html#elasticsearch.helpers.scan
 
+        The ``iterate()`` method should be preferred, as it provides similar
+        functionality using a point in time.
         """
         es = get_connection(self._using)
 
@@ -105,6 +109,54 @@ def delete(self):
             es.delete_by_query(index=self._index, body=self.to_dict(), **self._params)
         )
 
+    @contextlib.contextmanager
+    def point_in_time(self, keep_alive="1m"):
+        """
+        Open a point in time (pit) that can be used across several searches.
+
+        :arg keep_alive: the time to live for the point in time, renewed with each new search request
+
+        This method implements a context manager that returns a search object
+        configured to operate within the created pit. The following example
+        shows how to paginate through all the documents of an index::
+
+            page_size = 10
+            with Search(index="my-index")[:page_size].point_in_time() as s:
+                while True:
+                    r = s.execute()  # get a page of results
+                    // ... do something with r.hits
+
+                    if len(r.hits) < page_size:
+                        break  # we reached the end
+                    s = r.search_after()
+        """
+        es = get_connection(self._using)
+
+        pit = es.open_point_in_time(index=self._index or "*", keep_alive=keep_alive)
+        search = self.index().extra(pit={"id": pit["id"], "keep_alive": keep_alive})
+        if not search._sort:
+            search = search.sort("_shard_doc")
+        yield search
+        es.close_point_in_time(id=pit["id"])
+
+    def iterate(self, keep_alive="1m"):
+        """
+        Return a generator that iterates over all the documents matching the query.
+
+        :arg keep_alive: the time to live for the point in time, renewed with each new search request
+
+        This method uses a point in time to provide consistent results even when
+        the underlying index is changing. It should be preferred over ``scan()``.
+        """
+        with self.point_in_time(keep_alive=keep_alive) as s:
+            while True:
+                r = s.execute()
+                for hit in r:
+                    yield hit
+                if len(r.hits) == 0:
+                    break
+                s = r.search_after()
+
 
 class MultiSearch(MultiSearchBase):
     """

tests/test_integration/_async/test_search.py

@@ -179,6 +179,37 @@ async def test_search_after_no_results(async_data_client):
         await r.search_after()
 
 
+@pytest.mark.asyncio
+async def test_point_in_time(async_data_client):
+    page_size = 7
+    commits = []
+    async with AsyncSearch(index="flat-git")[:page_size].point_in_time(
+        keep_alive="30s"
+    ) as s:
+        pit_id = s._extra["pit"]["id"]
+        while True:
+            r = await s.execute()
+            commits += r.hits
+            if len(r.hits) < page_size:
+                break
+            s = r.search_after()
+            assert pit_id == s._extra["pit"]["id"]
+            assert "30s" == s._extra["pit"]["keep_alive"]
+
+    assert 52 == len(commits)
+    assert {d["_id"] for d in FLAT_DATA} == {c.meta.id for c in commits}
+
+
+@pytest.mark.asyncio
+async def test_iterate(async_data_client):
+    s = AsyncSearch(index="flat-git")
+
+    commits = [commit async for commit in s.iterate()]
+
+    assert 52 == len(commits)
+    assert {d["_id"] for d in FLAT_DATA} == {c.meta.id for c in commits}
+
+
 @pytest.mark.asyncio
 async def test_response_is_cached(async_data_client):
     s = Repository.search()

tests/test_integration/_sync/test_search.py

@@ -171,6 +171,35 @@ def test_search_after_no_results(data_client):
         r.search_after()
 
 
+@pytest.mark.sync
+def test_point_in_time(data_client):
+    page_size = 7
+    commits = []
+    with Search(index="flat-git")[:page_size].point_in_time(keep_alive="30s") as s:
+        pit_id = s._extra["pit"]["id"]
+        while True:
+            r = s.execute()
+            commits += r.hits
+            if len(r.hits) < page_size:
+                break
+            s = r.search_after()
+            assert pit_id == s._extra["pit"]["id"]
+            assert "30s" == s._extra["pit"]["keep_alive"]
+
+    assert 52 == len(commits)
+    assert {d["_id"] for d in FLAT_DATA} == {c.meta.id for c in commits}
+
+
+@pytest.mark.sync
+def test_iterate(data_client):
+    s = Search(index="flat-git")
+
+    commits = [commit for commit in s.iterate()]
+
+    assert 52 == len(commits)
+    assert {d["_id"] for d in FLAT_DATA} == {c.meta.id for c in commits}
+
+
 @pytest.mark.sync
 def test_response_is_cached(data_client):
     s = Repository.search()

utils/run-unasync.py

@@ -72,6 +72,7 @@ def main(check=False):
         "async_sleep": "sleep",
         "assert_awaited_once_with": "assert_called_once_with",
         "pytest_asyncio": "pytest",
+        "asynccontextmanager": "contextmanager",
     }
     rules = [
         unasync.Rule(