I'm migrating my system from Sphinx Search, and there are a couple of operators that are not available to Solr, which are available in Sphinx.
I would love to see the following added to the Dismax parser:
1. Exact match. This might be tricky to get right, since it requires work on the index side as well, but in Sphinx, you can do a query such as [ =running walking ], and running will have stemming off, while walking will have it on.
2. Term quorum. In Sphinx and some commercial search engines (like Recommind, Westlaw and Lexis), you can do a search such as [ (cat dog goat)/15 ], and find the three words within 15 terms of each other. I think this is possible in the backend via the span query, but there's no front end option for it, so it's quite hard to reveal to users.
3. Word order. Being able to say, "this term before that one, and this other term before the next" is something else in Sphinx that span queries support, but is missing in the query parser. Would be great to get this in too.
These seem like the three biggest missing operators in Solr to me. I would love to help move these forward if there is any way I can help.
 At least, I think it does. There's some discussion of one way of doing exact match like support in SOLR-2866.
|1.||Add query operator, index structure, and analyzer for "exact match" searching||Open||Unassigned|
|2.||Add an operator to edismax for word order (Proximity / NEAR)||Open||Unassigned||