fix(full-text-search): fix fuzzy extended to withdraw wrong results (#51)

Author: Viatorus

packages/full-text-search/spec/generic/search/fuzzy.spec.ts

@@ -132,9 +132,9 @@ describe("fuzzy query", () => {
       });
     }
     let query = new QB().fuzzy("body", "web").prefixLength(1).fuzziness(1).extended(true).build();
-    assertMatches(fts, query, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
+    assertMatches(fts, query, [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
 
     query = new QB().match("body", "web").prefixLength(1).fuzziness(1).extended(true).build();
-    assertMatches(fts, query, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
+    assertMatches(fts, query, [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
   });
 });

packages/full-text-search/src/index_searcher.ts

@@ -356,6 +356,17 @@ function fuzzySearch(query: ANY, root: InvertedIndex.Index) {
     let index = stack.pop();
     let treeTerms = treeStack.pop();
 
+    // Check if fuzzy should be extended.
+    if (extended) {
+      if (treeTerms.length === fuzzy.length) {
+        extend_fuzzy = levenshteinDistance(fuzzy, treeTerms);
+      } else {
+        extend_fuzzy = extend_fuzzy <= fuzziness && treeTerms.length >= fuzzy.length
+          ? extend_fuzzy
+          : 1e10;
+      }
+    }
+
     // Compare tokens if they are in near distance.
     if (index.df !== undefined) {
       let matched = false;
@@ -378,15 +389,6 @@ function fuzzySearch(query: ANY, root: InvertedIndex.Index) {
       }
     }
 
-    // Check if fuzzy should be extended.
-    if (extended && treeTerms.length === fuzzy.length) {
-      extend_fuzzy = levenshteinDistance(fuzzy, treeTerms);
-    } else {
-      extend_fuzzy = extended && extend_fuzzy <= fuzziness && treeTerms.length >= fuzzy.length
-        ? extend_fuzzy
-        : 1e10;
-    }
-
     // Iterate over all subtrees.
     // If token from tree is not longer than maximal distance.
     if ((treeTerms.length - fuzzy.length <= fuzziness) || extend_fuzzy <= fuzziness) {