I'm a bit of a performance freak. So if this strikes you as totally pointless, feel free to ignore me.
We've recently switched over to using a more complex DisMax search for some of our queries. In the process of measuring the performance impact, I noticed that my Query Cache had grown considerably with these new Queries. I made sure to use the same data set for before and after comparisons, and the same query set where I modified the queries to use the new search (qt=foo). Before, my queries took up an average of 800 bytes. Now they take an average of 3500 bytes. Overall, that will mean I will hold 75% less queries in my query cache then I used to. And the query cache is very important for performance. A little digging revealed that the extra memory usage was from the Query itself held in the cache key, not the results (doc ids). So, my question is, could we decrease the memory footprint of the queries in the cache, by *not* holding onto the Query object itself in the cache at all. Could we turn it into a canonical string that represents the query, and use that for the key in the cache? I'm assuming that would take up much less memory, at least in the case that I'm experiencing. Are there any benefits to be had here? Are there huge downsides I'm missing?
