sqme: zarr dask

odc/loader/_zarr.py

@@ -11,6 +11,7 @@
 import fsspec
 import numpy as np
 import xarray as xr
+from dask.delayed import Delayed, delayed
 from odc.geo.geobox import GeoBox
 from odc.geo.xr import ODCExtensionDa, ODCExtensionDs, xr_coords, xr_reproject
 
@@ -276,6 +277,10 @@ def read(
         return yx_roi, dst
 
 
+def _with_roi(xx: np.ndarray) -> tuple[tuple[slice, slice], np.ndarray]:
+    return (slice(None), slice(None)), xx
+
+
 class XrMemReaderDask:
     """
     Dask version of the reader.
@@ -288,7 +293,7 @@ def __init__(
         layer_name: str = "",
         idx: int = -1,
     ) -> None:
-        self._src = XrSource(src) if src is not None else None
+        self._src = XrSource(src, chunks="auto") if src is not None else None
         self._ctx = ctx
         self._layer_name = layer_name
         self._idx = idx
@@ -300,15 +305,19 @@ def read(
         *,
         selection: ReaderSubsetSelection | None = None,
         idx: tuple[int, ...] = (),
-    ) -> Any:
+    ) -> Delayed:
         assert self._src is not None
         assert isinstance(idx, tuple)
 
         xx = self._src.resolve(regen_coords=True)
         xx = _subset_src(xx, selection, cfg)
-        yy = xr_reproject(xx, dst_geobox, resampling=cfg.resampling, chunks={})
-        yx_roi = (slice(None), slice(None))
-        return yx_roi, yy.data
+        yy = xr_reproject(
+            xx,
+            dst_geobox,
+            resampling=cfg.resampling,
+            chunks=dst_geobox.shape.yx,
+        )
+        return delayed(_with_roi)(yy.data, dask_key_name=(self._layer_name, *idx))
 
     def open(
         self,

odc/loader/test_memreader.py

@@ -9,16 +9,28 @@
 import numpy as np
 import pytest
 import xarray as xr
+from dask import is_dask_collection
 from odc.geo.data import country_geom
 from odc.geo.gcp import GCPGeoBox
 from odc.geo.geobox import GeoBox
 from odc.geo.xr import ODCExtensionDa, ODCExtensionDs, rasterize
 
-from ._zarr import Context, XrMemReader, XrMemReaderDriver, raster_group_md
-from .types import FixedCoord, RasterGroupMetadata, RasterLoadParams, RasterSource
+from odc.loader._zarr import (
+    Context,
+    XrMemReader,
+    XrMemReaderDask,
+    XrMemReaderDriver,
+    raster_group_md,
+)
+from odc.loader.types import (
+    FixedCoord,
+    RasterGroupMetadata,
+    RasterLoadParams,
+    RasterSource,
+)
 
-# pylint: disable=missing-function-docstring,use-implicit-booleaness-not-comparison
-# pylint: disable=too-many-locals,too-many-statements,redefined-outer-name
+# pylint: disable=missing-function-docstring,use-implicit-booleaness-not-comparison,protected-access
+# pylint: disable=too-many-locals,too-many-statements,redefined-outer-name,import-outside-toplevel
 
 
 @pytest.fixture
@@ -70,6 +82,7 @@ def test_mem_reader(sample_ds: xr.Dataset) -> None:
 
     driver = XrMemReaderDriver(ds)
     assert driver.md_parser is not None
+    assert driver.dask_reader is not None
     md = driver.md_parser.extract(fake_item)
 
     assert isinstance(md, RasterGroupMetadata)
@@ -201,3 +214,16 @@ def test_memreader_zarr(sample_ds: xr.Dataset):
     assert isinstance(xx, np.ndarray)
     assert xx.shape == gbox[roi].shape.yx
     assert gbox == gbox[roi]
+
+    rdr = XrMemReaderDask().open(src, ctx, layer_name="xx", idx=0)
+    assert isinstance(rdr, XrMemReaderDask)
+
+    assert rdr._src._chunks == "auto"
+
+    fut = rdr.read(cfg, gbox)
+    assert is_dask_collection(fut)
+
+    roi, xx = fut.compute(scheduler="synchronous")
+    assert isinstance(xx, np.ndarray)
+    assert roi == (slice(None), slice(None))
+    assert xx.shape == gbox.shape.yx