Use orjson for faster JSONL output

CHANGELOG.md

@@ -7,6 +7,7 @@ _When adding new entries to the changelog, please include issue/PR numbers where
 
 ## Unreleased
 
+- diff: Use [orjson](https://github.com/ijl/orjson?tab=readme-ov-file#orjson) for faster JSON-Lines output. [#1019](https://github.com/koordinates/kart/pull/1019)
 - Upgrade to PDAL 2.7 [#1005](https://github.com/koordinates/kart/pull/1005)
 - Adds a `--drop-empty-geometry-features` option to `kart export`. [#1007](https://github.com/koordinates/kart/pull/1007)
 - Adds diagnostic output to Kart when `KART_DIAGNOSTICS=1` environment variable is set. [#1013](https://github.com/koordinates/kart/pull/1013)

kart/json_diff_writers.py

@@ -1,4 +1,4 @@
-import json
+import orjson
 import logging
 import threading
 from datetime import datetime, timedelta, timezone
@@ -19,7 +19,11 @@
 from kart.diff_structs import FILES_KEY, BINARY_FILE, DatasetDiff
 from kart.key_filters import DeltaFilter
 from kart.log import commit_obj_to_json
-from kart.output_util import dump_json_output, resolve_output_path
+from kart.output_util import (
+    dump_json_output,
+    resolve_output_path,
+    orjson_encode_default,
+)
 from kart.tabular.feature_output import feature_as_geojson, feature_as_json
 from kart.timestamps import datetime_to_iso8601_utc, timedelta_to_iso8601_tz
 
@@ -241,9 +245,13 @@ def __init__(self, *args, diff_estimate_accuracy=None, delta_filter=None, **kwar
         self._output_lock = threading.RLock()
 
     def dump(self, obj):
+        output: bytes = orjson.dumps(
+            obj,
+            default=orjson_encode_default,
+            option=orjson.OPT_APPEND_NEWLINE | orjson.OPT_NON_STR_KEYS,
+        )
         with self._output_lock:
-            json.dump(obj, self.fp, separators=self.separators)
-            self.fp.write("\n")
+            self.fp.buffer.write(output)
 
     def write_header(self):
         self.dump(

kart/output_util.py

@@ -8,17 +8,27 @@
 import types
 from pathlib import Path
 
+import orjson
 import pygments
 from pygments.lexers import JsonLexer
 
 from .wkt_lexer import WKTLexer
 
 _terminal_formatter = None
 
+# note: `json` and `orjson` libraries aren't quite interchangeable.
+#   * orjson is much faster, so we use it where we can
+#   * orjson doesn't support custom separators
+#   * orjson doesn't support iterencode(), so can't stream unbounded iterators to stdout :(
+ORJSON_OPTIONS = {
+    "compact": 0,  # orjson doesn't support custom separators, so extracompact and compact look identical
+    "extracompact": 0,
+    "pretty": orjson.OPT_INDENT_2,
+}
 JSON_PARAMS = {
     "compact": {},
-    "pretty": {"indent": 2},
     "extracompact": {"separators": (",", ":")},
+    "pretty": {"indent": 2},
 }
 
 
@@ -37,6 +47,19 @@ def __iter__(self):
         return itertools.chain(self._head, *self[:1])
 
 
+def orjson_encode_default(obj):
+    """
+    Hook to extend the default serialisation of `orjson.dumps()`
+    """
+    if isinstance(obj, tuple):
+        return list(obj)
+
+    if hasattr(obj, "__json__"):
+        return obj.__json__()
+
+    raise TypeError
+
+
 class ExtendedJsonEncoder(json.JSONEncoder):
     """A JSONEncoder that tries calling __json__() if it can't serialise an object another way."""
 

requirements/requirements.in

@@ -3,6 +3,7 @@ certifi
 click~=8.1.7
 docutils<0.18
 msgpack~=0.6.1
+orjson
 Pygments
 pymysql
 rst2txt

requirements/requirements.txt

@@ -22,7 +22,7 @@ certifi==2022.12.7
     #   reflink
 click==8.1.7
     # via -r requirements.in
-#cryptography==42.0.4
+#cryptography==43.0.1
     # via -r requirements/vendor-wheels.txt
 docutils==0.17.1
     # via
@@ -38,6 +38,8 @@ jsonschema==4.17.3
     # via -r requirements.in
 msgpack==0.6.2
     # via -r requirements.in
+orjson==3.10.11
+    # via -r requirements.in
 #psycopg2==2.9.9
     # via -r requirements/vendor-wheels.txt
 pycparser==2.21