From c96e8ab47c1dc59ad2934692b2fa2ff84c6c59c7 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Wed, 6 Sep 2023 14:44:42 +0200
Subject: [PATCH] db/simple/DirectorySave: optimize duplicate checks with
std::set
This reduces the CPU usage for loading a large database by more than 50%.
---
src/db/plugins/simple/DirectorySave.cxx | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/src/db/plugins/simple/DirectorySave.cxx b/src/db/plugins/simple/DirectorySave.cxx
index 010957e9d..8a3410c01 100644
--- a/src/db/plugins/simple/DirectorySave.cxx
+++ b/src/db/plugins/simple/DirectorySave.cxx
@@ -17,6 +17,9 @@
#include <fmt/format.h>
+#include <set>
+#include <string_view>
+
#include <string.h>
#define DIRECTORY_DIR "directory: "
@@ -109,9 +112,6 @@ ParseLine(Directory &directory, const char *line)
static Directory *
directory_load_subdir(LineReader &file, Directory &parent, std::string_view name)
{
- if (parent.FindChild(name) != nullptr)
- throw FmtRuntimeError("Duplicate subdirectory '{}'", name);
-
Directory *directory = parent.CreateChild(name);
try {
@@ -139,20 +139,24 @@ directory_load_subdir(LineReader &file, Directory &parent, std::string_view name
void
directory_load(LineReader &file, Directory &directory)
{
+ /* these sets are used to quickly check for duplicates,
+ avoiding linear lookups */
+ std::set<std::string_view> children, songs;
+
const char *line;
while ((line = file.ReadLine()) != nullptr &&
!StringStartsWith(line, DIRECTORY_END)) {
const char *p;
if ((p = StringAfterPrefix(line, DIRECTORY_DIR))) {
- directory_load_subdir(file, directory, p);
+ auto *child = directory_load_subdir(file, directory, p);
+
+ const std::string_view name = child->GetName();
+ if (!children.emplace(name).second)
+ throw FmtRuntimeError("Duplicate subdirectory '{}'", name);
} else if ((p = StringAfterPrefix(line, SONG_BEGIN))) {
const char *name = p;
- if (directory.FindSong(name) != nullptr)
- throw FmtRuntimeError("Duplicate song '{}'",
- name);
-
std::string target;
bool in_playlist = false;
auto detached_song = song_load(file, name,
@@ -163,6 +167,10 @@ directory_load(LineReader &file, Directory &directory)
song->target = std::move(target);
song->in_playlist = in_playlist;
+ if (!songs.emplace(song->filename).second)
+ throw FmtRuntimeError("Duplicate song '{}'",
+ name);
+
directory.AddSong(std::move(song));
} else if ((p = StringAfterPrefix(line, PLAYLIST_META_BEGIN))) {
const char *name = p;