Hi all,

In our project we like to have the ability to get search results scoped to one 'namespace' (as we call it). This can easily be achieved by using a filter or just an additional must-clause. For the spellchecker (and our autocompletion, which is a modified spellchecker), the story seems different. The spell checker index is created using a LuceneDictionary, which has a IndexReader as source. We would like to get (spellcheck/autocomplete) suggestions that are scoped to one namespace (i.e. field 'namespace' should have a particular value). With a single source index containing docs for all namespaces, it seems not possible to create a spellcheck index for each namespace the ordinary way. Q1: Is there a way to construct a LuceneDictionary from a subset of a single source index (all terms where namespace = %value%) ?

Another, maybe better solution is to customize the spellchecker by adding an additional namespace field to the spellchecker index. At query-time, an additional must-clause is added, scoping the suggestions to one (or more) namespace(s). The advantage of this is to have a singleton spellchecker (or at least the index reader) for all namespaces. This also means less open files by our application (imagine if there are over 1000 namespaces). Q2: Will there be a significant penalty (say more than 50% slower) for the additional must-clause at query time?

Q3: Or can you think of a better solution for this problem? :)

How we currently do it: we currently use Lucene 3.1 with Hibernate Search and we actually already have auto completion and spell checking scoped to one namespace. This is currently achieved by using index sharding, so each namespace has its own index and reader, and another for spell check and auto completion. Unfortunately there are some downsides to this: - Our faceting engine has no good support for multiple indexes, so faceting only works on a single namespace - Needs administration for mapping namespace identifier (String) to index number (integer) - The number of shards (and thus name spaces) is currently hardcoded. At this moment it is set to 100, and this means Hibernate Search opens up 100 index readers/writers, while only n<100 are in use. and therfore:
- Much open file descriptors
- Hard limit on number of namespaces

Therefore it seems better to switch back to having a single index for all namespaces.

Thanks!

Regards,
Elmer van Chastelet


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