(NOTE: this discussion probably makes more sense on solr-dev. future replies should probably go there, or in SOLR-334.)
: The parser is a quick hack I threw together, and any value source : factories should not be exposed to it. It seems like either : 1) a value source factory would expose the types it expects : or : 2) a value source factory would take a List<ValueSource> and throw a : ParseException if it didn't get what it expected : : Reflection might be fine if the cost of construction via reflection : ends up being small compared to the parsing itself. Another option is to assume that if people are writing their own ValueSoures and loading them into solr as plugins, they could write their "FunctionParser" subclass that knows about those ValueSoures and then register that FunctionParser -- the key being to make it easy to subclass a FunctionParser to add your own functions (without needing to cut/paste a tone of stuff like you do now) To me the key differentiator between something like this, and something like Tokenizer/TokenFilter factories is that with those, you want to be able to mix/match them at run time a lot -- but i'm guessing once you write a ValueSource and you want the function parser to use whenever it sees "foo(...)" that's not something you really need to change with each Solr install (or have one function parser for one request handler, and a different one for another reuqest handler) -Hoss
