Add an option to turn off density-weighting

When searching, Pagefind applies a heuristic that often works quite well
to boost pages with a higher density, i.e. a higher number of hits
divided by the number of words on the page. This is called "density
weighting".

In some instances, it is desirable, though, to just use the number of
hits directly, without dividing by the number of words on the page.

Let's support this via the search option `use_weighting`, which
default to `true` to maintain the current behavior.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

pagefind_web/src/lib.rs

@@ -210,7 +210,7 @@ pub fn filters(ptr: *mut SearchIndex) -> String {
 }
 
 #[wasm_bindgen]
-pub fn search(ptr: *mut SearchIndex, query: &str, filter: &str, sort: &str, exact: bool) -> String {
+pub fn search(ptr: *mut SearchIndex, query: &str, filter: &str, sort: &str, exact: bool, weighting: bool) -> String {
     let search_index = unsafe { Box::from_raw(ptr) };
 
     if let Some(generator_version) = search_index.generator_version.as_ref() {
@@ -225,7 +225,7 @@ pub fn search(ptr: *mut SearchIndex, query: &str, filter: &str, sort: &str, exac
     let (unfiltered_results, mut results) = if exact {
         search_index.exact_term(query, filter_set)
     } else {
-        search_index.search_term(query, filter_set)
+        search_index.search_term(query, filter_set, weighting)
     };
     let unfiltered_total = unfiltered_results.len();
     debug!({ format!("Raw total of {} results", unfiltered_total) });

pagefind_web/src/search.rs

@@ -175,6 +175,7 @@ impl SearchIndex {
         &self,
         term: &str,
         filter_results: Option<BitSet>,
+        weighting: bool,
     ) -> (Vec<usize>, Vec<PageSearchResult>) {
         debug!({
             format! {"Searching {:?}", term}
@@ -318,7 +319,7 @@ impl SearchIndex {
                 .map(|BalancedWordScore { balanced_score, .. }| balanced_score)
                 .sum::<f32>()
                 / 24.0)
-                / page.word_count as f32;
+                / (if weighting { page.word_count as f32 } else { 1.0 });
 
             let search_result = PageSearchResult {
                 page: page.hash.clone(),

pagefind_web_js/lib/coupled_search.ts

@@ -390,6 +390,7 @@ class PagefindInstance {
             verbose: false,
             filters: {},
             sort: {},
+            use_weighting: true,
             ...options,
         };
         const log = (str: string) => { if (options.verbose) console.log(str) };
@@ -443,7 +444,7 @@ class PagefindInstance {
         // pointer may have updated from the loadChunk calls
         ptr = await this.getPtr();
         let searchStart = Date.now();
-        let result = this.backend.search(ptr, term, filter_list, sort_list, exact_search) as string;
+        let result = this.backend.search(ptr, term, filter_list, sort_list, exact_search, options.use_weighting) as string;
         log(`Got the raw search result: ${result}`);
         let [unfilteredResultCount, all_results, filters, totalFilters] = result.split(/:([^:]*):(.*)__PF_UNFILTERED_DELIM__(.*)$/);
         let filterObj = this.parseFilters(filters);