Zend Lucene : index database data or not? -

i'll try indexing , zend lucene search first time , i'm wondering if datas database should indexed or not, considering performance. if when (in case) ?

my first goal index documents (pdf) search in.

in communications module of application develop, users can search communications entering keywords. app searches in subject , content of communications stored in database , now, index, searches in content of documents attached communications.

in way i've search in database , in index.

so i'm wondering if should index subject , content (e.g. : unindexed lucene field) of communication ? faster ? considering number of documents , communications increase quickly, , index too.

anyone has experience ?

yes, bringing in content want able search idea. run couple of problems searching both database , index.

first, performance worse. having run search against 2 different sources expected slower having searchable content in 1 place.

second, merging , ordering search results tends problematic. if making use of relevance score ordering (and if searching against full-text content, should be), merging results 2 different sources becomes difficult. you'll end less useful ordering, , performance hit.

especially if indexing (not storing) content considering adding index, there little reason not so, mind. being able search whatever need in index more powerful , faster.