[ZCM] [ZC] 753/ 1 Request "inconsistencies in the way to detect a missing attribute"

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Issue #753 Update (Request) "inconsistencies in the way to detect a missing attribute"
 Status Pending, Catalog/bug medium
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  http://collector.zope.org/Zope/753

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= Request - Entry #1 by olivluca on Jan 2, 2003 6:35 am

When catalogging/metadataing objects the catalog and plugin indexes try to detect a missing attribute in order to avoid indexing or storing metadata for a non existing attribute.
The problem is that each plugin index and the metadata extraction use different methods:

1) metadata (see recordify in Catalog.py) uses MV from Missing to indicate a missing attribute

2) UnIndex (and all indexes derived from it) uses an private attribute _marker defined as []

3) KeywordIndex uses () as a missing attribute and just catalogs everything


The problem is that if the attribute is provided by (e.g.) a python script, it's impossible for the python script to indicate a missing attribute, or it has to be done in several different methods:

a) for metadata is possible to return MV from Missing to indicate a missing attribute

b) for indexes deriving from UnIndex is impossible to indicate a missing attribute (since _marker is private)

c) for keyword indexes one has to return ()

d) even if it was possible to import the private _merker, it's not the same _marker for each index.

I think the solution would be to use the same value everywhere to detect a missing attribute, and this value should be useable from external method, like, e.g., MV from Missing, or a non private attribute imported from the same module.


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