diff --git a/extra_data/keydata.py b/extra_data/keydata.py
index 7ce1ea02..8860a6fa 100644
--- a/extra_data/keydata.py
+++ b/extra_data/keydata.py
@@ -444,3 +444,9 @@ def trains(self, keep_dims=False):
                     yield tid, ds[start]
 
                 start += count
+
+    def _pasha_functor_(self):
+        """Integration with pasha for map operations."""
+
+        from .pasha_functor import ExtraDataFunctor
+        return ExtraDataFunctor(self)
diff --git a/extra_data/pasha_functor.py b/extra_data/pasha_functor.py
new file mode 100644
index 00000000..74df6978
--- /dev/null
+++ b/extra_data/pasha_functor.py
@@ -0,0 +1,50 @@
+from os import getpid
+
+import numpy as np
+
+from . import DataCollection, KeyData
+from .read_machinery import split_trains
+
+
+class ExtraDataFunctor:
+    """Pasha functor for EXtra-data objects.
+
+    This functor wraps an EXtra-data DataCollection, SourceData or
+    KeyData and performs the map operation over its trains. The kernel
+    is passed the current train's index in the collection, the train ID
+    and the data mapping (for DataCollection) or data entry (for KeyData).
+    """
+
+    def __init__(self, obj):
+        self.obj = obj
+        self.n_trains = len(self.obj.train_ids)
+
+        # Save PID of parent process where the functor is created to
+        # close files as appropriately later on, see comment below.
+        self._parent_pid = getpid()
+
+    @classmethod
+    def wrap(cls, value):
+        if isinstance(value, (DataCollection, KeyData)):
+            return cls(value)
+
+    def split(self, num_workers):
+        return split_trains(self.n_trains, parts=num_workers)
+
+    def iterate(self, share):
+        subobj = self.obj.select_trains(np.s_[share])
+
+        # Older versions of HDF < 1.10.5 are not robust against sharing
+        # a file descriptor across threads or processes. If running in a
+        # different process than the functor was initially created in,
+        # close all file handles inherited from the parent collection to
+        # force re-opening them again in each child process.
+        if getpid() != self._parent_pid:
+            for f in subobj.files:
+                f.close()
+
+        index_it = range(*share.indices(self.n_trains))
+        data_it = subobj.trains()
+
+        for index, (train_id, data) in zip(index_it, data_it):
+            yield index, train_id, data
diff --git a/extra_data/reader.py b/extra_data/reader.py
index 7395b276..e558f921 100644
--- a/extra_data/reader.py
+++ b/extra_data/reader.py
@@ -347,6 +347,12 @@ def trains(self, devices=None, train_range=None, *, require_all=False,
         return iter(TrainIterator(dc, require_all=require_all,
                                   flat_keys=flat_keys, keep_dims=keep_dims))
 
+    def _pasha_functor_(self):
+        """Integration with pasha for map operations."""
+
+        from .pasha_functor import ExtraDataFunctor
+        return ExtraDataFunctor(self)
+
     def train_from_id(
         self, train_id, devices=None, *, flat_keys=False, keep_dims=False):
         """Get train data for specified train ID.