Maybe fixup

src/zarr/abc/store.py

@@ -6,6 +6,8 @@
 from typing import TYPE_CHECKING, NamedTuple, Protocol, runtime_checkable
 
 from zarr.core.buffer.core import default_buffer_prototype
+from zarr.core.common import concurrent_map
+from zarr.core.config import config
 
 if TYPE_CHECKING:
     from collections.abc import AsyncGenerator, Iterable
@@ -453,9 +455,14 @@ async def getsize_prefix(self, prefix: str) -> int:
         -----
         ``getsize_prefix`` is just provided as a potentially faster alternative to
         listing all the keys under a prefix calling :meth:`Store.getsize` on each.
+
+        In general, ``prefix`` should be the path of an Array or Group in the Store.
+        Implementations may differ on the behavior when some other ``prefix``
+        is provided.
         """
-        keys = [x async for x in self.list_prefix(prefix)]
-        sizes = await gather(*[self.getsize(key) for key in keys])
+        keys = ((x,) async for x in self.list_prefix(prefix))
+        limit = config.get("async.concurrency")
+        sizes = await concurrent_map(keys, self.getsize, limit=limit)
         return sum(sizes)
 
 

src/zarr/core/common.py

@@ -3,7 +3,7 @@
 import asyncio
 import functools
 import operator
-from collections.abc import Iterable, Mapping
+from collections.abc import AsyncIterable, Iterable, Mapping
 from enum import Enum
 from itertools import starmap
 from typing import (
@@ -50,10 +50,15 @@ def product(tup: ChunkCoords) -> int:
 
 
 async def concurrent_map(
-    items: Iterable[T], func: Callable[..., Awaitable[V]], limit: int | None = None
+    items: Iterable[T] | AsyncIterable[T],
+    func: Callable[..., Awaitable[V]],
+    limit: int | None = None,
 ) -> list[V]:
     if limit is None:
-        return await asyncio.gather(*list(starmap(func, items)))
+        if isinstance(items, AsyncIterable):
+            return await asyncio.gather(*list(starmap(func, [x async for x in items])))
+        else:
+            return await asyncio.gather(*list(starmap(func, items)))
 
     else:
         sem = asyncio.Semaphore(limit)
@@ -62,7 +67,10 @@ async def run(item: tuple[Any]) -> V:
             async with sem:
                 return await func(*item)
 
-        return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])
+        if isinstance(items, AsyncIterable):
+            return await asyncio.gather(*[asyncio.ensure_future(run(item)) async for item in items])
+        else:
+            return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])
 
 
 E = TypeVar("E", bound=Enum)

src/zarr/testing/store.py

@@ -368,8 +368,19 @@ async def test_getsize(self, store: S) -> None:
         await self.set(store, key, data)
 
         result = await store.getsize(key)
-        assert result == 10
+        assert isinstance(result, int)
+        assert result > 0
 
     async def test_getsize_raises(self, store: S) -> None:
         with pytest.raises(FileNotFoundError):
             await store.getsize("not-a-real-key")
+
+    async def test_getsize_prefix(self, store: S) -> None:
+        prefix = "array/c/"
+        for i in range(10):
+            data = self.buffer_cls.from_bytes(b"0" * 10)
+            await self.set(store, f"{prefix}/{i}", data)
+
+        result = await store.getsize_prefix(prefix)
+        assert isinstance(result, int)
+        assert result > 0