Add regression test

.gitignore

@@ -50,7 +50,8 @@ nosetests.xml
 dask-worker-space/
 
 # asv environments
-.asv
+asv_bench/.asv
+asv_bench/pkgs
 
 # Translations
 *.mo
@@ -68,7 +69,7 @@ dask-worker-space/
 
 # xarray specific
 doc/_build
-generated/
+doc/generated/
 xarray/tests/data/*.grib.*.idx
 
 # Sync tools

xarray/tests/test_backends.py

@@ -13,6 +13,7 @@
 import tempfile
 import uuid
 import warnings
+from collections import Counter
 from collections.abc import Generator, Iterator, Mapping
 from contextlib import ExitStack
 from io import BytesIO
@@ -2990,6 +2991,184 @@ def test_chunked_cftime_datetime(self) -> None:
             assert original.chunks == actual.chunks
 
 
+def attach_counter(f):
+    counter = Counter()
+
+    def wrapper(self, *args):
+        if f.__name__ in ["__contains__", "__getitem__"] and args[0] == "zarr.json":
+            # ignore this spam
+            pass
+        else:
+            print(f"Calling {f.__name__} with {args}")
+            counter.update(args[slice(1)]) if args else counter.update(("foo",))
+        return f(self, *args)
+
+    wrapper.counter = counter
+    return wrapper
+
+
+class CountingStore(KVStoreV3):
+    def __init__(self):
+        super().__init__({})
+        self.instrumented_methods = [
+            "__iter__",
+            "__contains__",
+            "__setitem__",
+            "__getitem__",
+            "listdir",
+            "list_prefix",
+        ]
+
+    @attach_counter
+    def __iter__(self):
+        return super().__iter__()
+
+    @attach_counter
+    def listdir(self, *args, **kwargs):
+        return super().listdir(*args, **kwargs)
+
+    @attach_counter
+    def list_prefix(self, *args, **kwargs):
+        return super().list_prefix(*args, **kwargs)
+
+    @attach_counter
+    def __contains__(self, key) -> bool:
+        return super().__contains__(key)
+
+    @attach_counter
+    def __getitem__(self, key):
+        return super().__getitem__(key)
+
+    @attach_counter
+    def __setitem__(self, *args, **kwargs):
+        return super().__setitem__(*args, **kwargs)
+
+    def summarize(self):
+        summary = {}
+        for method in self.instrumented_methods:
+            name = method.strip("__")
+            if counter := getattr(self, method).counter:
+                summary[name] = sum(counter.values())
+            else:
+                summary[name] = 0
+        return summary
+
+    def reset(self):
+        for method in self.instrumented_methods:
+            getattr(self, method).counter.clear()
+
+
+@requires_zarr
+@pytest.mark.skipif(not have_zarr_v3, reason="requires zarr version 3")
+class TestInstrumentedZarrStore:
+    @contextlib.contextmanager
+    def create_zarr_target(self):
+        yield CountingStore()
+
+    def check_requests(self, expected, store):
+        summary = store.summarize()
+        for k in summary:
+            assert summary[k] <= expected[k], summary
+        store.reset()
+
+    def test_append(self) -> None:
+        original = Dataset({"foo": ("x", [1])}, coords={"x": [0]})
+        modified = Dataset({"foo": ("x", [2])}, coords={"x": [1]})
+        with self.create_zarr_target() as store:
+            original.to_zarr(store)
+            expected = {
+                "iter": 2,
+                "contains": 9,
+                "setitem": 9,
+                "getitem": 6,
+                "listdir": 2,
+                "list_prefix": 2,
+            }
+            self.check_requests(expected, store)
+
+            modified.to_zarr(store, mode="a", append_dim="x")
+            # v2024.03.0: {'iter': 6, 'contains': 2, 'setitem': 5, 'getitem': 10, 'listdir': 6, 'list_prefix': 0}
+            # 6057128b: {'iter': 5, 'contains': 2, 'setitem': 5, 'getitem': 10, "listdir": 5, "list_prefix": 0}
+            expected = {
+                "iter": 2,
+                "contains": 9,
+                "setitem": 8,
+                "getitem": 6,
+                "listdir": 2,
+                "list_prefix": 2,
+            }
+            self.check_requests(expected, store)
+
+            modified.to_zarr(store, mode="a-", append_dim="x")
+            expected = {
+                "iter": 2,
+                "contains": 2,
+                "setitem": 5,
+                "getitem": 6,
+                "listdir": 2,
+                "list_prefix": 2,
+            }
+            self.check_requests(expected, store)
+
+            with open_dataset(store, engine="zarr") as actual:
+                assert_identical(
+                    actual, xr.concat([original, modified, modified], dim="x")
+                )
+
+    @requires_dask
+    def test_region_write(self) -> None:
+        ds = Dataset({"foo": ("x", [1, 2, 3])}, coords={"x": [0, 1, 2]}).chunk()
+        with self.create_zarr_target() as store:
+            ds.to_zarr(store, mode="w", compute=False)
+            expected = {
+                "iter": 2,
+                "contains": 7,
+                "setitem": 9,
+                "getitem": 6,
+                "listdir": 2,
+                "list_prefix": 4,
+            }
+            self.check_requests(expected, store)
+
+            ds.to_zarr(store, region={"x": slice(None)})
+            # v2024.03.0: {'iter': 5, 'contains': 2, 'setitem': 1, 'getitem': 6, 'listdir': 5, 'list_prefix': 0}
+            # 6057128b: {'iter': 4, 'contains': 2, 'setitem': 1, 'getitem': 5, 'listdir': 4, 'list_prefix': 0}
+            expected = {
+                "iter": 2,
+                "contains": 2,
+                "setitem": 1,
+                "getitem": 3,
+                "listdir": 2,
+                "list_prefix": 0,
+            }
+            self.check_requests(expected, store)
+
+            ds.to_zarr(store, region="auto")
+            # v2024.03.0: {'iter': 6, 'contains': 4, 'setitem': 1, 'getitem': 11, 'listdir': 6, 'list_prefix': 0}
+            # 6057128b: {'iter': 4, 'contains': 2, 'setitem': 1, 'getitem': 7, 'listdir': 4, 'list_prefix': 0}
+            expected = {
+                "iter": 2,
+                "contains": 2,
+                "setitem": 1,
+                "getitem": 5,
+                "listdir": 2,
+                "list_prefix": 0,
+            }
+            self.check_requests(expected, store)
+
+            expected = {
+                "iter": 1,
+                "contains": 2,
+                "setitem": 0,
+                "getitem": 5,
+                "listdir": 1,
+                "list_prefix": 0,
+            }
+            with open_dataset(store, engine="zarr") as actual:
+                assert_identical(actual, ds)
+            self.check_requests(expected, store)
+
+
 @requires_zarr
 class TestZarrDictStore(ZarrBase):
     @contextlib.contextmanager