WIP: RemoteButler.find_dataset

python/lsst/daf/butler/remote_butler/_remote_butler.py

@@ -48,8 +48,8 @@
 from .._storage_class import StorageClass
 from .._timespan import Timespan
 from ..datastore import DatasetRefURIs
-from ..dimensions import DataId, DimensionConfig, DimensionUniverse
-from ..registry import CollectionArgType, Registry, RegistryDefaults
+from ..dimensions import DataCoordinate, DataId, DimensionConfig, DimensionUniverse, SerializedDataCoordinate
+from ..registry import CollectionArgType, NoDefaultCollectionError, Registry, RegistryDefaults
 from ..transfers import RepoExportContext
 from ._config import RemoteButlerConfigModel
 
@@ -101,6 +101,26 @@ def dimensions(self) -> DimensionUniverse:
         self._dimensions = DimensionUniverse(config)
         return self._dimensions
 
+    def _simplify_dataId(self, dataId: DataId | None) -> SerializedDataCoordinate | None:
+        """Take a generic Data ID and convert it to a serializable form.
+
+        Parameters
+        ----------
+        dataId : `dict`, `None`, `DataCoordinate`
+            The data ID to serialize.
+
+        Returns
+        -------
+        data_id : `SerializedDataCoordinate` or `None`
+            A serializable form.
+        """
+        if dataId is None:
+            return None
+        if isinstance(dataId, DataCoordinate):
+            return dataId.to_simple()
+        # Assume we can treat it as a dict.
+        return SerializedDataCoordinate(dataId=dataId)
+
     def getDatasetType(self, name: str) -> DatasetType:
         # Docstring inherited.
         raise NotImplementedError()
@@ -196,6 +216,17 @@ def find_dataset(
         datastore_records: bool = False,
         **kwargs: Any,
     ) -> DatasetRef | None:
+        if collections is None:
+            if not self.collections:
+                raise NoDefaultCollectionError(
+                    "No collections provided to find_dataset, and no defaults from butler construction."
+                )
+            collections = self.collections
+        # Temporary hack. Assume strings for collections. In future
+        # want to construct CollectionWildcard and filter it through collection
+        # cache to generate list of collection names.
+        # collection_strings = [str(c) for c in collections]
+
         raise NotImplementedError()
 
     def retrieveArtifacts(

python/lsst/daf/butler/remote_butler/server/_server.py

@@ -33,9 +33,15 @@
 from functools import cache
 from typing import Any
 
-from fastapi import Depends, FastAPI
+from fastapi import Depends, FastAPI, Query
 from fastapi.middleware.gzip import GZipMiddleware
-from lsst.daf.butler import Butler, SerializedDatasetType
+from lsst.daf.butler import (
+    Butler,
+    DataCoordinate,
+    SerializedDataCoordinate,
+    SerializedDatasetRef,
+    SerializedDatasetType,
+)
 
 from ._factory import Factory
 
@@ -56,6 +62,26 @@ def factory_dependency() -> Factory:
     return Factory(butler=_make_global_butler())
 
 
+def unpack_dataId(butler: Butler, data_id: SerializedDataCoordinate | None) -> DataCoordinate | None:
+    """Convert the serialized dataId back to full DataCoordinate.
+
+    Parameters
+    ----------
+    butler : `lsst.daf.butler.Butler`
+        The butler to use for registry and universe.
+    data_id : `SerializedDataCoordinate` or `None`
+        The serialized form.
+
+    Returns
+    -------
+    dataId : `DataCoordinate` or `None`
+        The DataId usable by registry.
+    """
+    if data_id is None:
+        return None
+    return DataCoordinate.from_simple(data_id, registry=butler.registry)
+
+
 @app.get("/butler/v1/universe", response_model=dict[str, Any])
 def get_dimension_universe(factory: Factory = Depends(factory_dependency)) -> dict[str, Any]:
     """Allow remote client to get dimensions definition."""
@@ -78,3 +104,26 @@ def get_dataset_type(
     butler = factory.create_butler()
     datasetType = butler.get_dataset_type(dataset_type_name)
     return datasetType.to_simple()
+
+
+# Not yet supported: TimeSpan is not yet a pydantic model.
+# collections parameter assumes client-side has resolved regexes.
+@app.post(
+    "/butler/v1/find_dataset/{datasetType}",
+    summary="Retrieve this dataset definition from collection, dataset type, and dataId",
+    response_model=SerializedDatasetRef,
+    response_model_exclude_unset=True,
+    response_model_exclude_defaults=True,
+    response_model_exclude_none=True,
+)
+def find_dataset(
+    datasetType: str,
+    dataId: SerializedDataCoordinate | None = None,
+    collections: list[str] | None = Query(None),
+    factory: Factory = Depends(factory_dependency),
+) -> SerializedDatasetRef | None:
+    collection_query = collections if collections else None
+
+    butler = factory.create_butler()
+    ref = butler.find_dataset(datasetType, dataId=unpack_dataId(butler, dataId), collections=collection_query)
+    return ref.to_simple() if ref else None