Hi Daniel, You said inputs are "human-generated" and outputs are "lucene objects". So my question is what does the below query mean. Does this fall under human-generated one or lucene.?
http://localhost:8983/solr/collection1/select?q=*%3A*&wt=xml&indent=true Thanks, Vivek On Fri, Jun 20, 2014 at 3:55 PM, Daniel Collins <danwcoll...@gmail.com> wrote: > Alexandre's response is very thorough, so I'm really simplifying things, I > confess but here's my "query parsers for dummies". :) > > In terms of inputs/outputs, a QueryParser takes a string (generally assumed > to be "human generated" i.e. something a user might type in, so maybe a > sentence, a set of words, the format can vary) and outputs a Lucene Query > object ( > > http://lucene.apache.org/core/4_8_1/core/org/apache/lucene/search/Query.html > ), > which in fact is a kind of "tree" (again, I'm simplifying I know) since a > query can contain nested expressions. > > So very loosely its a translator from a human-generated query into the > structure that Lucene can handle. There are several different query > parsers since they all use different input syntax, and ways of handling > different constructs (to handle A and B, should the user type "+A +B" or "A > and B" or just "A B" for example), and have different levels of support for > the various Query structures that Lucene can handle: SpanQuery, FuzzyQuery, > PhraseQuery, etc. > > We for example use an XML-based query parser. Why (you might well ask!), > well we had an already used and supported query syntax of our own, which > our users understood, so we couldn't use an off the shelf query parser. We > could have built our own in Java, but for a variety of reasons we parse our > queries in a front-end system ahead of Solr (which is C++-based), so we > needed an interim format to pass queries to Solr that was as near to a > Lucene Query object as we could get (and there was an existing XML parser > to save us starting from square one!). > > As part of that Query construction (but independent of which QueryParser > you use), Solr will also make use of a set of Tokenizers and Filters ( > > https://cwiki.apache.org/confluence/display/solr/Understanding+Analyzers,+Tokenizers,+and+Filters > ) > but that's more to do with dealing with the terms in the query (so in my > examples above, is A a real word, does it need stemming, lowercasing, > removing because its a stopword, etc). >
