Fixed #30190 -- Added JSONL serializer.

AUTHORS

@@ -52,6 +52,7 @@ answer newbie questions, and generally made Django that much better:
     Alex Robbins <[email protected]>
     Alexey Boriskin <[email protected]>
     Alexey Tsivunin <[email protected]>
+    Ali Vakilzade <[email protected]>
     Aljosa Mohorovic <[email protected]>
     Amit Chakradeo <https://amit.chakradeo.net/>
     Amit Ramon <[email protected]>

django/core/serializers/__init__.py

@@ -28,6 +28,7 @@
     "python": "django.core.serializers.python",
     "json": "django.core.serializers.json",
     "yaml": "django.core.serializers.pyyaml",
+    "jsonl": "django.core.serializers.jsonl",
 }
 
 _serializers = {}

django/core/serializers/jsonl.py

@@ -0,0 +1,57 @@
+"""
+Serialize data to/from JSON Lines
+"""
+
+import json
+
+from django.core.serializers.base import DeserializationError
+from django.core.serializers.json import DjangoJSONEncoder
+from django.core.serializers.python import (
+    Deserializer as PythonDeserializer, Serializer as PythonSerializer,
+)
+
+
+class Serializer(PythonSerializer):
+    """Convert a queryset to JSON Lines."""
+    internal_use_only = False
+
+    def _init_options(self):
+        self._current = None
+        self.json_kwargs = self.options.copy()
+        self.json_kwargs.pop('stream', None)
+        self.json_kwargs.pop('fields', None)
+        self.json_kwargs.pop('indent', None)
+        self.json_kwargs['separators'] = (',', ': ')
+        self.json_kwargs.setdefault('cls', DjangoJSONEncoder)
+        self.json_kwargs.setdefault('ensure_ascii', False)
+
+    def start_serialization(self):
+        self._init_options()
+
+    def end_object(self, obj):
+        # self._current has the field data
+        json.dump(self.get_dump_object(obj), self.stream, **self.json_kwargs)
+        self.stream.write("\n")
+        self._current = None
+
+    def getvalue(self):
+        # Grandparent super
+        return super(PythonSerializer, self).getvalue()
+
+
+def Deserializer(stream_or_string, **options):
+    """Deserialize a stream or string of JSON data."""
+    if isinstance(stream_or_string, bytes):
+        stream_or_string = stream_or_string.decode()
+    if isinstance(stream_or_string, (bytes, str)):
+        stream_or_string = stream_or_string.split("\n")
+
+    for line in stream_or_string:
+        if not line.strip():
+            continue
+        try:
+            yield list(PythonDeserializer([json.loads(line), ], **options))[0]
+        except (GeneratorExit, DeserializationError):
+            raise
+        except Exception as exc:
+            raise DeserializationError() from exc

docs/releases/3.2.txt

@@ -215,7 +215,10 @@ Security
 Serialization
 ~~~~~~~~~~~~~
 
-* ...
+* The new :ref:`JSONL <serialization-formats-jsonl>` serializer allows using
+  the JSON Lines format with :djadmin:`dumpdata` and :djadmin:`loaddata`. This
+  can be useful for populating large databases because data is loaded line by
+  line into memory, rather than being loaded all at once.
 
 Signals
 ~~~~~~~

docs/topics/serialization.txt

@@ -160,11 +160,14 @@ Identifier  Information
 
 ``json``    Serializes to and from JSON_.
 
+``jsonl``   Serializes to and from JSONL_.
+
 ``yaml``    Serializes to YAML (YAML Ain't a Markup Language). This
             serializer is only available if PyYAML_ is installed.
 ==========  ==============================================================
 
 .. _json: https://json.org/
+.. _jsonl: http://jsonlines.org/
 .. _PyYAML: https://pyyaml.org/
 
 XML
@@ -307,6 +310,24 @@ The JSON serializer uses ``DjangoJSONEncoder`` for encoding. A subclass of
 
 .. _ecma-262: https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
 
+.. _serialization-formats-jsonl:
+
+JSONL
+-----
+
+.. versionadded:: 3.2
+
+*JSONL* stands for *JSON Lines*. With this format, objects are separated by new
+lines, and each line contains a valid JSON object. JSONL serialized data look
+like this::
+
+    { "pk": "4b678b301dfd8a4e0dad910de3ae245b", "model": "sessions.session", "fields": { ... }}
+    { "pk": "88bea72c02274f3c9bf1cb2bb8cee4fc", "model": "sessions.session", "fields": { ... }}
+    { "pk": "9cf0e26691b64147a67e2a9f06ad7a53", "model": "sessions.session", "fields": { ... }}
+
+JSONL can be useful for populating large databases, since the data can be
+processed line by line, rather than being loaded into memory all at once.
+
 YAML
 ----