search: fix subtle bug with some newest-first text search

Due to the way the range queries work for newest-first searches, we can
have a situation where the MDB_SET_RANGE gets placed on either the
correct place or just after the correct place. To position the cursor
correctly, we jump back one if the search result prefix doesn't match.

ndb.c

@@ -121,6 +121,8 @@ static void ndb_print_text_search_result(struct ndb_txn *txn,
 	printf("\n%s\n\n---\n", ndb_note_str(note, &note->content).str);
 }
 
+int ndb_print_search_keys(struct ndb_txn *txn);
+
 int main(int argc, char *argv[])
 {
 	struct ndb *ndb;
@@ -199,6 +201,11 @@ int main(int argc, char *argv[])
 	} else if (argc == 3 && !strcmp(argv[1], "import")) {
 		map_file(argv[2], &data, &data_len);
 		ndb_process_events(ndb, (const char *)data, data_len);
+		ndb_process_client_events(ndb, (const char *)data, data_len);
+	} else if (argc == 2 && !strcmp(argv[1], "print-search-keys")) {
+		ndb_begin_query(ndb, &txn);
+		ndb_print_search_keys(&txn);
+		ndb_end_query(&txn);
 	} else {
 		return usage();
 	}

nostrdb.c

@@ -2473,6 +2473,38 @@ static void ndb_print_text_search_key(struct ndb_text_search_key *key)
 						    key->note_id);
 }
 
+static int ndb_prefix_matches(struct ndb_text_search_result *result,
+			      struct ndb_word *search_word)
+{
+	// Empty strings shouldn't happen but let's
+	if (result->key.str_len < 2 || search_word->word_len < 2)
+		return 0;
+
+	// make sure we at least have two matching prefix characters. exact
+	// matches are nice but range searches allow us to match prefixes as
+	// well. A double-char prefix is suffient, but maybe we could up this
+	// in the future.
+	// 
+	// TODO: How are we handling utf-8 prefix matches like
+	// japanese?
+	//
+	if (   result->key.str[0] != tolower(search_word->word[0])
+	    && result->key.str[1] != tolower(search_word->word[1])
+	    )
+		return 0;
+
+	// count the number of prefix-matched characters. This will be used
+	// for ranking search results
+	result->prefix_chars = prefix_count(result->key.str,
+					    result->key.str_len,
+					    search_word->word,
+					    search_word->word_len);
+
+	if (result->prefix_chars <= (int)((double)search_word->word_len / 1.5)) 
+		return 0;
+
+	return 1;
+}
 
 // This is called when scanning the full text search index. Scanning stops
 // when we no longer have a prefix match for the word
@@ -2483,7 +2515,10 @@ static int ndb_text_search_next_word(MDB_cursor *cursor, MDB_cursor_op op,
 	MDB_cursor_op order_op)
 {
 	struct cursor key_cursor;
+	//struct ndb_text_search_key search_key;
 	MDB_val v;
+	int retries;
+	retries = -1;
 
 	make_cursor(k->mv_data, k->mv_data + k->mv_size, &key_cursor);
 
@@ -2504,6 +2539,15 @@ static int ndb_text_search_next_word(MDB_cursor *cursor, MDB_cursor_op op,
 		}
 	}
 
+retry:
+	retries++;
+	/*
+	printf("continuing from ");
+	if (ndb_unpack_text_search_key(k->mv_data, k->mv_size, &search_key)) {
+		ndb_print_text_search_key(&search_key);
+	} else { printf("??"); }
+	printf("\n");
+	*/
 
 	make_cursor(k->mv_data, k->mv_data + k->mv_size, &key_cursor);
 
@@ -2533,32 +2577,17 @@ static int ndb_text_search_next_word(MDB_cursor *cursor, MDB_cursor_op op,
 		return 0;
 	}
 
-	// Empty strings shouldn't happen but let's
-	if (result->key.str_len < 2 || search_word->word_len < 2)
-		return 0;
-
-	// make sure we at least have two matching prefix characters. exact
-	// matches are nice but range searches allow us to match prefixes as
-	// well. A double-char prefix is suffient, but maybe we could up this
-	// in the future.
-	// 
-	// TODO: How are we handling utf-8 prefix matches like
-	// japanese?
-	//
-	if (   result->key.str[0] != tolower(search_word->word[0])
-	    && result->key.str[1] != tolower(search_word->word[1])
-	    )
-		return 0;
-
-	// count the number of prefix-matched characters. This will be used
-	// for ranking search results
-	result->prefix_chars = prefix_count(result->key.str,
-					    result->key.str_len,
-					    search_word->word,
-					    search_word->word_len);
-
-	if (result->prefix_chars <= (int)((double)search_word->word_len / 1.5)) 
-		return 0;
+	if (!ndb_prefix_matches(result, search_word)) {
+		// we should only do this if we're going in reverse
+		if (retries == 0 && op == MDB_SET_RANGE && order_op == MDB_PREV) {
+			// if set range worked and our key exists, it should be
+			// the one right before this one
+			if (mdb_cursor_get(cursor, k, &v, MDB_PREV))
+				goto retry;
+		} else {
+			return 0;
+		}
+	}
 
 	// Unpack the remaining text search key, we will need this information
 	// when building up our search results.
@@ -4439,3 +4468,30 @@ void ndb_config_set_ingest_filter(struct ndb_config *config,
 	config->ingest_filter = fn;
 	config->filter_context = filter_ctx;
 }
+
+// used by ndb.c
+int ndb_print_search_keys(struct ndb_txn *txn)
+{
+	MDB_cursor *cur;
+	MDB_val k, v;
+	int i;
+	struct ndb_text_search_key search_key;
+
+	if (mdb_cursor_open(txn->mdb_txn, txn->lmdb->dbs[NDB_DB_NOTE_TEXT], &cur))
+		return 0;
+
+	i = 1;
+	while (mdb_cursor_get(cur, &k, &v, MDB_NEXT) == 0) {
+		if (!ndb_unpack_text_search_key(k.mv_data, k.mv_size, &search_key)) {
+			fprintf(stderr, "error decoding key %d\n", i);
+			continue;
+		}
+
+		ndb_print_text_search_key(&search_key);
+		printf("\n");
+
+		i++;
+	}
+
+	return 1;
+}

test.c

@@ -961,6 +961,9 @@ static void test_fulltext()
 
 	ndb_begin_query(ndb, &txn);
 	ndb_text_search(&txn, "Jump Over", &results, NULL);
+	fprintf(stderr, "num results %d\n", results.num_results);
+	assert(results.num_results == 2);
+	assert(!strcmp(results.results[0].key.str, "jumped"));
 	ndb_end_query(&txn);
 
 	ndb_destroy(ndb);