Merge branch 'modify-lhcb-writer-compression' into 'master'

Remove LHCb mdf writer compression by default

See merge request !3331

PyConf/python/PyConf/application.py

@@ -62,11 +62,18 @@ ROOT_KEY = 'ROOT'
 FILE_TYPES = {MDF_KEY, ROOT_KEY}
 
 
-def mdf_writer(path, location, compression=2):
-    """Return an MDF writer which writes a single  TES `location` to `path`."""
+def mdf_writer(path, location, compression=0):
+    """Return an MDF writer which writes a single  TES `location` to `path`.
+
+    By default no compression is used, since `IOSvc` does not currently support
+    compressed inputs and also because there is already compression internally
+    to the "DstData" raw banks (which dominate when no detector raw banks are
+    written out). See https://gitlab.cern.ch/lhcb/LHCb/-/issues/163.
+    """
+
     return LHCb__MDFWriter(
         BankLocation=location,
-        Compress=compression,  # TODO compression ???
+        Compress=compression,
         Connection="file://{}".format(path),
     )