On Sat, Jul 15, 2017 at 8:12 PM, Uwe Schindler <u...@thetaphi.de> wrote: > That is the "Solr" answer. But it is slow like hell. > > In Lucene there is a natove query named FieldValueQuery already for this. > It requires DocValues enabled for the field. > > IMHO, the best and fastest variant (also to Solr users) is to add a separate > multivalued string field named 'fieldnames' where you index all field named > that have a value. After that you can query on this using the field name. > Elasticsearch is doing the field name approach for exists/not exists by > default.
The catch is, you usually have to analyse a field to determine whether it has a value. Apparently Elasticsearch's field existence query does not do this, so it considers blank text to be a value, which is not the same as what the user expected when they did the query. We *were* using FieldValueQuery, but since moving to Lucene 6 we have stopped using uninverting reader, so that option doesn't cover all fields, and fields like "content" aren't really practical to put in DocValues... The approach to add a fieldnames field works, but is fiddly at indexing-time, because now you have to use TokenStream for all fields, so that you can read one token from each field to test whether there is one before you add the whole document. I guess it's at least easier to understand how it works at query-time. TX --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
