// Merge facets across multiple search services
static void MergeFacets(IDictionary <string, IList <FacetResult> > singleServiceFacets, MultiSearchFacets mergedFacets)
{
foreach (KeyValuePair <string, IList <FacetResult> > resultFacets in singleServiceFacets)
{
string fieldName = resultFacets.Key;
IList <FacetResult> serviceFacets = resultFacets.Value;
if (mergedFacets.Facets.TryGetValue(fieldName, out List <MultiSearchFacet> multiServiceFacets))
{
// If a facet can be merged into an existing multi-service facet, combine the counts
// Otherwise, add a new multi-service facet matching the existing facet
foreach (FacetResult facet in serviceFacets)
{
bool foundFacet = false;
foreach (MultiSearchFacet multiServiceFacet in multiServiceFacets)
{
if (multiServiceFacet.CanMergeFacet(facet))
{
foundFacet = true;
multiServiceFacet.Count += facet.Count.Value;
break;
}
}
if (!foundFacet)
{
multiServiceFacets.Add(new MultiSearchFacet(facet));
}
}
}
else
{
// Initialize the multi-service facet list with the facets from this service for this field
mergedFacets.Facets.Add(fieldName, serviceFacets.Select(f => new MultiSearchFacet(f)).ToList());
}
}
}
// Run the query and combine results across multiple services
static async Task <(int, List <MultiSearchResult>, MultiSearchFacets)> RunQueryAsync(string query, int pageNumber, int pageSize, string searchFields, string facets, List <Service> services)
{
// Page results from all services
var searchResults = new List <IAsyncEnumerator <MultiSearchResultsPage> >();
foreach (Service service in services)
{
IAsyncEnumerable <MultiSearchResultsPage> response = SearchAsync(service, query, pageSize, searchFields, facets);
searchResults.Add(response.GetAsyncEnumerator());
}
// Merge each individual page from every service
// Sort the combined page by result score
int currentPageNumber = 0;
var currentPage = new List <MultiSearchResult>();
var mergedFacets = new MultiSearchFacets();
do
{
// Combine the current page of results from each service
// If the service has no more results, it is discarded
var resultPages = new List <MultiSearchResultsPage>();
var nextSearchResults = new List <IAsyncEnumerator <MultiSearchResultsPage> >();
foreach (IAsyncEnumerator <MultiSearchResultsPage> pageEnumerator in searchResults)
{
if (await pageEnumerator.MoveNextAsync())
{
resultPages.Add(pageEnumerator.Current);
nextSearchResults.Add(pageEnumerator);
}
}
searchResults = nextSearchResults;
var mergedSearchResults = new List <MultiSearchResult>();
foreach (MultiSearchResultsPage resultPage in resultPages)
{
foreach (SearchResult <BookModel> result in resultPage.Page)
{
mergedSearchResults.Add(new MultiSearchResult {
Service = resultPage.Service, Result = result
});
}
if (resultPage.Facets != null)
{
MergeFacets(resultPage.Facets, mergedFacets);
}
}
// Sort the combined pages by score descending
mergedSearchResults.Sort((a, b) =>
{
MultiSearchResult resultA = a;
MultiSearchResult resultB = b;
if (resultA.Result.Score.HasValue && resultB.Result.Score.HasValue)
{
return(resultB.Result.Score.Value.CompareTo(resultA.Result.Score.Value));
}
if (resultA.Result.Score.HasValue && !resultB.Result.Score.HasValue)
{
return(-1);
}
if (!resultA.Result.Score.HasValue && resultB.Result.Score.HasValue)
{
return(1);
}
return(0);
});
// Return sub-pages of results from the combined page
foreach (MultiSearchResult mergedSearchResult in mergedSearchResults)
{
currentPage.Add(mergedSearchResult);
if (currentPage.Count == pageSize)
{
if (currentPageNumber == pageNumber)
{
return(currentPageNumber, currentPage, mergedFacets);
}
currentPage.Clear();
currentPageNumber++;
}
}
}while (searchResults.Any());
// Return any leftover results as the last page
return(currentPageNumber, currentPage, mergedFacets);
}
