feat: integrate limit to last (#145)

* feat: integrate limit_to_last changes from #57 to async

* fix: whitespace in docs

* fix: whitespace in docs

google/cloud/firestore_v1/async_collection.py

@@ -13,9 +13,6 @@
 # limitations under the License.
 
 """Classes for representing collections for the Google Cloud Firestore API."""
-import warnings
-
-
 from google.cloud.firestore_v1.base_collection import (
     BaseCollectionReference,
     _auto_id,
@@ -130,17 +127,26 @@ async def list_documents(
         async for i in iterator:
             yield _item_to_document_ref(self, i)
 
-    async def get(
-        self, transaction=None
-    ) -> AsyncGenerator[async_document.DocumentSnapshot, Any]:
-        """Deprecated alias for :meth:`stream`."""
-        warnings.warn(
-            "'Collection.get' is deprecated:  please use 'Collection.stream' instead.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        async for d in self.stream(transaction=transaction):
-            yield d  # pytype: disable=name-error
+    async def get(self, transaction=None) -> list:
+        """Read the documents in this collection.
+
+        This sends a ``RunQuery`` RPC and returns a list of documents
+        returned in the stream of ``RunQueryResponse`` messages.
+
+        Args:
+            transaction
+                (Optional[:class:`~google.cloud.firestore_v1.transaction.Transaction`]):
+                An existing transaction that this query will run in.
+
+        If a ``transaction`` is used and it already has write operations
+        added, this method cannot be used (i.e. read-after-write is not
+        allowed).
+
+        Returns:
+            list: The documents in this collection that match the query.
+        """
+        query = self._query()
+        return await query.get(transaction=transaction)
 
     async def stream(
         self, transaction=None

google/cloud/firestore_v1/async_query.py

@@ -18,12 +18,11 @@
 a :class:`~google.cloud.firestore_v1.collection.Collection` and that can be
 a more common way to create a query than direct usage of the constructor.
 """
-import warnings
-
 from google.cloud.firestore_v1.base_query import (
     BaseQuery,
     _query_response_to_snapshot,
     _collection_group_query_response_to_snapshot,
+    _enum_from_direction,
 )
 
 from google.cloud.firestore_v1 import _helpers
@@ -94,6 +93,7 @@ def __init__(
         field_filters=(),
         orders=(),
         limit=None,
+        limit_to_last=False,
         offset=None,
         start_at=None,
         end_at=None,
@@ -105,23 +105,51 @@ def __init__(
             field_filters=field_filters,
             orders=orders,
             limit=limit,
+            limit_to_last=limit_to_last,
             offset=offset,
             start_at=start_at,
             end_at=end_at,
             all_descendants=all_descendants,
         )
 
-    async def get(
-        self, transaction=None
-    ) -> AsyncGenerator[async_document.DocumentSnapshot, None]:
-        """Deprecated alias for :meth:`stream`."""
-        warnings.warn(
-            "'AsyncQuery.get' is deprecated:  please use 'AsyncQuery.stream' instead.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        async for d in self.stream(transaction=transaction):
-            yield d
+    async def get(self, transaction=None) -> list:
+        """Read the documents in the collection that match this query.
+
+        This sends a ``RunQuery`` RPC and returns a list of documents
+        returned in the stream of ``RunQueryResponse`` messages.
+
+        Args:
+            transaction
+                (Optional[:class:`~google.cloud.firestore_v1.transaction.Transaction`]):
+                An existing transaction that this query will run in.
+
+        If a ``transaction`` is used and it already has write operations
+        added, this method cannot be used (i.e. read-after-write is not
+        allowed).
+
+        Returns:
+            list: The documents in the collection that match this query.
+        """
+        is_limited_to_last = self._limit_to_last
+
+        if self._limit_to_last:
+            # In order to fetch up to `self._limit` results from the end of the
+            # query flip the defined ordering on the query to start from the
+            # end, retrieving up to `self._limit` results from the backend.
+            for order in self._orders:
+                order.direction = _enum_from_direction(
+                    self.DESCENDING
+                    if order.direction == self.ASCENDING
+                    else self.ASCENDING
+                )
+            self._limit_to_last = False
+
+        result = self.stream(transaction=transaction)
+        result = [d async for d in result]
+        if is_limited_to_last:
+            result = list(reversed(result))
+
+        return result
 
     async def stream(
         self, transaction=None
@@ -152,6 +180,12 @@ async def stream(
             :class:`~google.cloud.firestore_v1.async_document.DocumentSnapshot`:
             The next document that fulfills the query.
         """
+        if self._limit_to_last:
+            raise ValueError(
+                "Query results for queries that include limit_to_last() "
+                "constraints cannot be streamed. Use Query.get() instead."
+            )
+
         parent_path, expected_prefix = self._parent._parent_info()
         response_iterator = await self._client._firestore_api.run_query(
             request={

google/cloud/firestore_v1/base_collection.py

@@ -205,6 +205,10 @@ def order_by(self, field_path, **kwargs) -> NoReturn:
     def limit(self, count) -> NoReturn:
         """Create a limited query with this collection as parent.
 
+        .. note::
+           `limit` and `limit_to_last` are mutually exclusive.
+           Setting `limit` will drop previously set `limit_to_last`.
+
         See
         :meth:`~google.cloud.firestore_v1.query.Query.limit` for
         more information on this method.
@@ -220,6 +224,24 @@ def limit(self, count) -> NoReturn:
         query = self._query()
         return query.limit(count)
 
+    def limit_to_last(self, count):
+        """Create a limited to last query with this collection as parent.
+        .. note::
+           `limit` and `limit_to_last` are mutually exclusive.
+           Setting `limit_to_last` will drop previously set `limit`.
+        See
+        :meth:`~google.cloud.firestore_v1.query.Query.limit_to_last`
+        for more information on this method.
+        Args:
+            count (int): Maximum number of documents to return that
+                match the query.
+        Returns:
+            :class:`~google.cloud.firestore_v1.query.Query`:
+            A limited to last query.
+        """
+        query = self._query()
+        return query.limit_to_last(count)
+
     def offset(self, num_to_skip) -> NoReturn:
         """Skip to an offset in a query with this collection as parent.
 

google/cloud/firestore_v1/base_query.py

@@ -98,6 +98,8 @@ class BaseQuery(object):
             The "order by" entries to use in the query.
         limit (Optional[int]):
             The maximum number of documents the query is allowed to return.
+        limit_to_last (Optional[bool]):
+            Denotes whether a provided limit is applied to the end of the result set.
         offset (Optional[int]):
             The number of results to skip.
         start_at (Optional[Tuple[dict, bool]]):
@@ -146,6 +148,7 @@ def __init__(
         field_filters=(),
         orders=(),
         limit=None,
+        limit_to_last=False,
         offset=None,
         start_at=None,
         end_at=None,
@@ -156,6 +159,7 @@ def __init__(
         self._field_filters = field_filters
         self._orders = orders
         self._limit = limit
+        self._limit_to_last = limit_to_last
         self._offset = offset
         self._start_at = start_at
         self._end_at = end_at
@@ -170,6 +174,7 @@ def __eq__(self, other):
             and self._field_filters == other._field_filters
             and self._orders == other._orders
             and self._limit == other._limit
+            and self._limit_to_last == other._limit_to_last
             and self._offset == other._offset
             and self._start_at == other._start_at
             and self._end_at == other._end_at
@@ -224,6 +229,7 @@ def select(self, field_paths) -> "BaseQuery":
             field_filters=self._field_filters,
             orders=self._orders,
             limit=self._limit,
+            limit_to_last=self._limit_to_last,
             offset=self._offset,
             start_at=self._start_at,
             end_at=self._end_at,
@@ -294,6 +300,7 @@ def where(self, field_path, op_string, value) -> "BaseQuery":
             orders=self._orders,
             limit=self._limit,
             offset=self._offset,
+            limit_to_last=self._limit_to_last,
             start_at=self._start_at,
             end_at=self._end_at,
             all_descendants=self._all_descendants,
@@ -345,21 +352,51 @@ def order_by(self, field_path, direction=ASCENDING) -> "BaseQuery":
             field_filters=self._field_filters,
             orders=new_orders,
             limit=self._limit,
+            limit_to_last=self._limit_to_last,
             offset=self._offset,
             start_at=self._start_at,
             end_at=self._end_at,
             all_descendants=self._all_descendants,
         )
 
     def limit(self, count) -> "BaseQuery":
-        """Limit a query to return a fixed number of results.
-
-        If the current query already has a limit set, this will overwrite it.
+        """Limit a query to return at most `count` matching results.
 
+        If the current query already has a `limit` set, this will override it.
+        .. note::
+           `limit` and `limit_to_last` are mutually exclusive.
+           Setting `limit` will drop previously set `limit_to_last`.
         Args:
             count (int): Maximum number of documents to return that match
                 the query.
+        Returns:
+            :class:`~google.cloud.firestore_v1.query.Query`:
+            A limited query. Acts as a copy of the current query, modified
+            with the newly added "limit" filter.
+        """
+        return self.__class__(
+            self._parent,
+            projection=self._projection,
+            field_filters=self._field_filters,
+            orders=self._orders,
+            limit=count,
+            limit_to_last=False,
+            offset=self._offset,
+            start_at=self._start_at,
+            end_at=self._end_at,
+            all_descendants=self._all_descendants,
+        )
 
+    def limit_to_last(self, count):
+        """Limit a query to return the last `count` matching results.
+        If the current query already has a `limit_to_last`
+        set, this will override it.
+        .. note::
+           `limit` and `limit_to_last` are mutually exclusive.
+           Setting `limit_to_last` will drop previously set `limit`.
+        Args:
+            count (int): Maximum number of documents to return that match
+                the query.
         Returns:
             :class:`~google.cloud.firestore_v1.query.Query`:
             A limited query. Acts as a copy of the current query, modified
@@ -371,6 +408,7 @@ def limit(self, count) -> "BaseQuery":
             field_filters=self._field_filters,
             orders=self._orders,
             limit=count,
+            limit_to_last=True,
             offset=self._offset,
             start_at=self._start_at,
             end_at=self._end_at,
@@ -398,6 +436,7 @@ def offset(self, num_to_skip) -> "BaseQuery":
             field_filters=self._field_filters,
             orders=self._orders,
             limit=self._limit,
+            limit_to_last=self._limit_to_last,
             offset=num_to_skip,
             start_at=self._start_at,
             end_at=self._end_at,

google/cloud/firestore_v1/collection.py

@@ -13,8 +13,6 @@
 # limitations under the License.
 
 """Classes for representing collections for the Google Cloud Firestore API."""
-import warnings
-
 from google.cloud.firestore_v1.base_collection import (
     BaseCollectionReference,
     _auto_id,
@@ -121,14 +119,26 @@ def list_documents(self, page_size=None) -> Generator[Any, Any, None]:
         )
         return (_item_to_document_ref(self, i) for i in iterator)
 
-    def get(self, transaction=None) -> Generator[document.DocumentSnapshot, Any, None]:
-        """Deprecated alias for :meth:`stream`."""
-        warnings.warn(
-            "'Collection.get' is deprecated:  please use 'Collection.stream' instead.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        return self.stream(transaction=transaction)
+    def get(self, transaction=None) -> list:
+        """Read the documents in this collection.
+
+        This sends a ``RunQuery`` RPC and returns a list of documents
+        returned in the stream of ``RunQueryResponse`` messages.
+
+        Args:
+            transaction
+                (Optional[:class:`~google.cloud.firestore_v1.transaction.Transaction`]):
+                An existing transaction that this query will run in.
+
+        If a ``transaction`` is used and it already has write operations
+        added, this method cannot be used (i.e. read-after-write is not
+        allowed).
+
+        Returns:
+            list: The documents in this collection that match the query.
+        """
+        query = query_mod.Query(self)
+        return query.get(transaction=transaction)
 
     def stream(
         self, transaction=None