Read AMR domains lazily

yt/data_objects/index_subobjects/octree_subset.py

@@ -1,3 +1,4 @@
+import abc
 from contextlib import contextmanager
 from functools import cached_property
 from itertools import product, repeat
@@ -33,7 +34,7 @@ def cc_cache_func(self, dobj):
     return cc_cache_func
 
 
-class OctreeSubset(YTSelectionContainer):
+class OctreeSubset(YTSelectionContainer, abc.ABC):
     _spatial = True
     _num_ghost_zones = 0
     _type_name = "octree_subset"
@@ -51,12 +52,17 @@ def __init__(self, base_region, domain, ds, num_zones=2, num_ghost_zones=0):
         self.domain_id = domain.domain_id
         self.ds = domain.ds
         self._index = self.ds.index
-        self.oct_handler = domain.oct_handler
         self._last_mask = None
         self._last_selector_id = None
         self.base_region = base_region
         self.base_selector = base_region.selector
 
+    @property
+    @abc.abstractmethod
+    def oct_handler(self):
+        # In charge of returning the oct_handler
+        pass
+
     def __getitem__(self, key):
         tr = super().__getitem__(key)
         try:

yt/frontends/art/data_structures.py

@@ -727,6 +727,10 @@ def _is_valid(cls, filename: str, *args, **kwargs) -> bool:
 
 
 class ARTDomainSubset(OctreeSubset):
+    @property
+    def oct_handler(self):
+        return self.domain.oct_handler
+
     def fill(self, content, ftfields, selector):
         """
         This is called from IOHandler. It takes content
@@ -798,7 +802,11 @@ def __init__(self, ds, nvar, oct_handler, domain_id):
         self._level_count = None
         self._level_oct_offsets = None
         self._level_child_offsets = None
-        self.oct_handler = oct_handler
+        self._oct_handler = oct_handler
+
+    @property
+    def oct_handler(self):
+        return self._oct_handler
 
     @property
     def level_count(self):

yt/frontends/artio/data_structures.py

@@ -34,7 +34,7 @@ def __init__(self, base_region, sfc_start, sfc_end, oct_handler, ds):
         self.field_parameters = {}
         self.sfc_start = sfc_start
         self.sfc_end = sfc_end
-        self.oct_handler = oct_handler
+        self._oct_handler = oct_handler
         self.ds = ds
         self._last_mask = None
         self._last_selector_id = None
@@ -43,6 +43,10 @@ def __init__(self, base_region, sfc_start, sfc_end, oct_handler, ds):
         self.base_region = base_region
         self.base_selector = base_region.selector
 
+    @property
+    def oct_handler(self):
+        return self._oct_handler
+
     @property
     def min_ind(self):
         return self.sfc_start