how to get total hit count for each Searchable?

[xin liu]

Hi,

I have individual index files for Audio, Image and PDF files. We build common 
meta fields for these different data types. When I search for a string, I want 
the search to return mixed search results from these 3 different index based on 
relevancy. So I use ParallelMultiSearcher class to do the search. But I also 
wants to know individual hit count for each individual index type. For example, 
I want to get:
    Mixed together total hit count: 103, with the first 10 HitItem.
    Total hit in Audio: 73
    Total hit in Image: 17
    Total hit in PDF: 13

Right now, I'm doing the following way:
1. Gets one Searchable instance for Audio, one for Image, and one for PDF index;
2. construct ParallelMultiSearcher s with above 3 Searchable as parameters; 
call its search to get total hit count and first 10 hit items;
3. Call Audio searchable to get total hit count in Audio;
4. Call Image searchable to get total hit count for Image;
5. Call PDF searchable to get total hit count for Image.

So, Lucene will need do 6 search operations for these 3 index. Definitely, the 
performance will be an issue.

Any better solution for this? Thanks!

Tony