Hello Lucene users,
I'm rather new to lucene and java but have done work with other
search engines some time before.
Right now I'm trying my hands (and luck) on a 'search as you type'-
sort of high performance search a la GoogleSuggest.
There meanwhile are on the net, a number of examples for such script-
driven forms that are suggesting new possible input to the user with
every keystroke. Mostly for some sort of products.
Some instances are even combining the input from two or more text
fields or giving fault tolerant feedback.
According to occasional references on this list some people have
already tried to implement such a search with lucene but did they
succeed?
My first idea was to run every completed token of the request
(current user input) through a spellchecker and expand an incomplete
token to a PrefixQuery.
Example:
artist:'beetles'
title:'yellow submar'
Alternative terms for 'beetles' and 'yellow' would be looked up by
Spellcheckers for their respective fields and 'submar' being the last
token of the active textfield with no trailing whitespace would be
turned into a PrefixQuery.
And of course the performance considerations have to be of major
concern with these searches.
I'm currently dealing with the problem that short prefixes are
resulting in BooleanQuery$TooManyClauses exceptions.
That's why I've thought of discarding them in favour of extra fields
with the first bigrams and trigrams of every indexed token.
artist:'the beatles'
artist_start:'be bea' ('the' being a stopword)
title:'yellow submarine'
title_start:'ye yel su sub'
Every PrefixQuery of length 2 or 3 could thus be turned into a simple
TermQuery on the appropriate field. (With searches for 1-letter-
prefixes altogether discarded.)
I've seen Otis Gospodnetic suggesting the very same strategy in a
former thread but I have no idea about how I could possibly add these
extra fields.
Normally an IndexWriter uses only one default Analyzer for all its
tokenizing businesses. And while it is appearantly possible to supply
a certain other instance when adding a specific document there seems
to be no way to use different analyzers on different fields within
one document.
Could this be done in one pass at all, or do I have to copy all
documents from one index to a new one, parsing field tokens and
adding new fields on the 2nd go?
I'd appreciate every hint and suggestion on what classes and methods
to write for this purpose because I definitely lack a knack when it
comes to OOP.
Thank You In Advance,
Steffen
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