1 files changed, 40 insertions, 8 deletions

diff --git a/searchlib/src/vespa/searchlib/attribute/dfa_fuzzy_matcher.h b/searchlib/src/vespa/searchlib/attribute/dfa_fuzzy_matcher.h
index fcba13f85a4..8e5b3ce0ccd 100644
--- a/searchlib/src/vespa/searchlib/attribute/dfa_fuzzy_matcher.h
+++ b/searchlib/src/vespa/searchlib/attribute/dfa_fuzzy_matcher.h
@@ -5,6 +5,7 @@
 #include "dfa_string_comparator.h"
 #include <vespa/vespalib/datastore/atomic_entry_ref.h>
 #include <vespa/vespalib/fuzzy/levenshtein_dfa.h>
+#include <iostream>
 
 namespace search::attribute {
 
@@ -17,22 +18,53 @@ namespace search::attribute {
 class DfaFuzzyMatcher {
 private:
     vespalib::fuzzy::LevenshteinDfa _dfa;
-    std::vector<uint32_t> _successor;
+    std::vector<uint32_t>           _successor;
+    std::vector<uint32_t>           _prefix;
+    uint32_t                        _prefix_size;
+    bool                            _cased;
 
+    const char* skip_prefix(const char* word) const;
 public:
-    DfaFuzzyMatcher(std::string_view target, uint8_t max_edits, bool cased, vespalib::fuzzy::LevenshteinDfa::DfaType dfa_type);
+    DfaFuzzyMatcher(std::string_view target, uint8_t max_edits, uint32_t prefix_size, bool cased, vespalib::fuzzy::LevenshteinDfa::DfaType dfa_type);
     ~DfaFuzzyMatcher();
 
+    bool is_match(const char *word) const;
+
+    /*
+     * If prefix size is nonzero then this variant of is_match()
+     * should only be called with words that starts with the extracted
+     * prefix of the target word.
+     *
+     * Caller must position iterator at right location using lower bound
+     * functionality in the dictionary.
+     */
     template <typename DictionaryConstIteratorType>
     bool is_match(const char* word, DictionaryConstIteratorType& itr, const DfaStringComparator::DataStoreType& data_store) {
-        auto match = _dfa.match(word, _successor);
-        if (match.matches()) {
-            return true;
+        if (_prefix_size > 0) {
+            word = skip_prefix(word);
+            if (_prefix.size() < _prefix_size) {
+                if (*word == '\0') {
+                    return true;
+                }
+                _successor.resize(_prefix.size());
+                _successor.emplace_back(1);
+            } else {
+                _successor.resize(_prefix.size());
+                auto match = _dfa.match(word, _successor);
+                if (match.matches()) {
+                    return true;
+                }
+            }
         } else {
-            DfaStringComparator cmp(data_store, _successor);
-            itr.seek(vespalib::datastore::AtomicEntryRef(), cmp);
-            return false;
+            _successor.clear();
+            auto match = _dfa.match(word, _successor);
+            if (match.matches()) {
+                return true;
+            }
         }
+        DfaStringComparator cmp(data_store, _successor);
+        itr.seek(vespalib::datastore::AtomicEntryRef(), cmp);
+        return false;
     }
 };