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From Chris Hostetter <hossman_luc...@fucit.org>
Subject Re: searching portions of an index
Date Wed, 21 Dec 2005 19:04:06 GMT

: document might be accessible by different users. I want to implement this
: without indexing a document multiple times. The approach I thought of was to
: use a field that is indexed, as well as stored in the index, which contains
: the ids of all the users that can access the document. I could then use

The "Best" solution really depends on what determines if a user can view a
document.  If the set of documents visible to user "Bob" is based on
a set of document properties (ie: bob can view any documents in the
"reports" category that have an access level of "5" or less), then you can
store the properties bob is restricted to anywhere, and at search time
look them up and make a Filter out of them to apply to Bob's searches.
(ie: a ChainedFilter containing a simple TermFilter on the category field
and a RangeFilter on the level field)

If the set of documents viewable by a given person is truely an arbitrary
list of document identifiers stored in a DB somewhere, then build a Filter
that knows how to access that list, and sets the bits only on the document
identifiers in that list.

As always: accessing the stored fields of every document in your index
from a Filter is not a good idea -- make sure the identifier field is
indexed, and use the FieldCache to loop over all of the keys for all of
the docs


The key elements to any approach being:

  1) Don't store the lsit of users in the docs, that seems like a real
     waste.
  2) Use a Filter for each user (or if possible, group of users that have
     access permissions in common)
  3) Cache those Filters using something like CachingWrapperFilter (if
     your Index doesn't change very often, but you have lots of users, you
     may want a differnet caching approach that lets you expire Filters
     without closing the IndexReader.




-Hoss


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