Redesigning a search engine, what design patterns to apply

I'm really stuck here. I'm trying to do add a new database in addition to a current one. I'm going to use a factory pattern to select the right database control like this:

private AssetStoresFactory assetStoresFactory;

AssetStore assetStore = assetStoreFactory.getAssetStore(query);
assetStore.search(search);

public AssetStore getAssetStore(String query){
 AssetStore assetStore;
 if (qualifiesForStoreA(query))
  assetStore = new AssetStoreA(); 
 else 
  assetStore = new AssetStoreB(); 
 return assetStore;
}


AssetStore A
.....
Results search(AssetSearch search) {
 AssetSearchOperation o = new AssetSearchOperationA(search);
}
.....


AssetStore B
.....
Results search(AssetSearch search) {
 AssetSearchOperation o = new AssetSearchOperationB(search);
}
..... 

Now the real problem lies here. The current approach to perform searches is like this:

                    _______________________
                    | BaseSearchOperation |
                    | ___________________ |
                    | abstract search()   |
                    -----------------------
                             ᴧ 
                             |
                     ____________________
                     | StreamingSupport | 
                     |__________________|
                             ᴧ 
                             | 
                    ______________________
                    |AssetSearchOperation|
                    |____________________|

Now there is code to query the current database in all of the above classes and this needs to be removed and isolated. I can't get my head around how this can be done. Note that anonymous implementations of AssetSearchOperation override StreamingSupport. Any help is appreciated! If you need more information, please do ask!