Hi,
we've successfully implemented suggestion of search terms using facet
prefixing with Solr 4.0. However, with lots of unique index terms we've
encountered performance problems (long running queries) and even
exceptions: "Too many values for UnInvertedField faceting on field
textbody".
We must provide suggestions based on a prefix entered by the user. The
solution should use the terms from an indexed text field. Furthermore
the suggestions must be filtered according to some specified filter
queries.
Do you have any performance tips for facet prefixing or know how to
avoid the above exception even in the case of many unique terms?
What is causing the above exception: a) the total number of unique terms
in the field or b) the number of unique terms in the field of a single
document
If b), is there a way to find such documents easily? Do you know how
many unique terms can be handled without problems by facet prefixing?
I've read the blog post
http://www.searchworkings.org/blog/-/blogs/different-ways-to-make-auto-suggestions-with-solr
which describes NGrams as another possible approach to implement
suggestions with filtering. I would expect that this approach provides
better query performance (at the cost of increased index size). However
I haven't found detailed information how to implement it. I know how to
configure a field for ngrams and how to perform a query using that
field. But the results just give me the document but not the matched
terms. Or am I expected to use a stored field and inspect its value?
I also found this blog post where the Highlighter is used in combination
with ngrams to provide suggestions:
http://solr.pl/en/2013/02/25/autocomplete-on-multivalued-fields-using-highlighting/
Can this be used to get the suggested terms from a document? What about
performance? Will such an approach perform better than facet prefixing
for large text fields with lots of unique terms?
Any hints appreciated.
Thank you,
Andreas
