Merge pull request #671 from davidhassell/cache-compressed

In `cf.read`, skip caching elements from compression index variables.

cf/__init__.py

@@ -193,7 +193,7 @@
     )
 
 # Check the version of cfdm
-_minimum_vn = "1.10.1.0"
+_minimum_vn = "1.10.1.1"
 _maximum_vn = "1.10.2.0"
 _cfdm_version = Version(cfdm.__version__)
 if not Version(_minimum_vn) <= _cfdm_version < Version(_maximum_vn):

cf/read_write/netcdf/netcdfread.py

@@ -154,6 +154,7 @@ def _create_data(
         parent_ncvar=None,
         coord_ncvar=None,
         cfa_term=None,
+        compression_index=False,
     ):
         """Create data for a netCDF or CFA-netCDF variable.
 
@@ -181,6 +182,12 @@ def _create_data(
 
                 .. versionadded:: 3.15.0
 
+           compression_index: `bool`, optional
+                True if the data being created are compression
+                indices.
+
+                .. versionadded:: 3.15.2
+
         :Returns:
 
             `Data`
@@ -201,12 +208,19 @@ def _create_data(
             # one dask chunk
             if data.npartitions == 1:
                 data._cfa_set_write(True)
-
-            if self.implementation.get_construct_type(construct) != "field":
-                # Only cache values from non-field data, on the
-                # assumption that field data is, in general, so large
-                # that finding the cached values takes too long. See
-                # method `_cache_data_elements` for details.
+            if (
+                not compression_index
+                and self.implementation.get_construct_type(construct)
+                != "field"
+            ):
+                # Only cache values from non-field data and
+                # non-compression-index data, on the assumptions that:
+                #
+                # a) Field data is, in general, so large that finding
+                #    the cached values takes too long.
+                #
+                # b) Cached values are never really required for
+                #    compression index data.
                 self._cache_data_elements(data, ncvar)
 
             return data

docs/source/installation.rst

@@ -201,7 +201,7 @@ Required
 * `cftime <https://pypi.org/project/cftime/>`_, version 1.6.2 or newer
   (note that this package may be installed with netCDF4).
 
-* `cfdm <https://pypi.org/project/cfdm/>`_, version 1.10.1.0 or up to,
+* `cfdm <https://pypi.org/project/cfdm/>`_, version 1.10.1.1 or up to,
   but not including, 1.10.2.0.
 
 * `cfunits <https://pypi.org/project/cfunits/>`_, version 3.3.6 or newer.

requirements.txt

@@ -1,7 +1,7 @@
 netCDF4>=1.5.4
 cftime>=1.6.2
 numpy>=1.22
-cfdm>=1.10.1.0, <1.10.2.0
+cfdm>=1.10.1.1, <1.10.2.0
 psutil>=0.6.0
 cfunits>=3.3.6
 dask>=2022.12.1