Database: Add an index on the parent path

So we can quickly query the items in a parent directory

This uses a custom slite3 function, which means that when downgrading the client,
or using another tool to add entries in the database, any insertion in the metadata
table will produce an error: "unknown function: parent_hash()"
(This will crash the client 2.5)

src/common/syncjournaldb.cpp

@@ -24,6 +24,7 @@
 #include <QUrl>
 #include <QDir>
 #include <sqlite3.h>
+#include <cstring>
 
 #include "common/syncjournaldb.h"
 #include "version.h"
@@ -342,6 +343,15 @@ bool SyncJournalDb::checkConnect()
         return sqlFail("Set PRAGMA case_sensitivity", pragma1);
     }
 
+    sqlite3_create_function(_db.sqliteDb(), "parent_hash", 1, SQLITE_UTF8 | SQLITE_DETERMINISTIC, nullptr,
+                                [] (sqlite3_context *ctx,int, sqlite3_value **argv) {
+                                    auto text = reinterpret_cast<const char*>(sqlite3_value_text(argv[0]));
+                                    const char *end = std::strrchr(text, '/');
+                                    if (!end) end = text;
+                                    sqlite3_result_int64(ctx, c_jhash64(reinterpret_cast<const uint8_t*>(text),
+                                                                        end - text, 0));
+                                }, nullptr, nullptr);
+
     /* Because insert is so slow, we do everything in a transaction, and only need one call to commit */
     startTransaction();
 
@@ -682,6 +692,16 @@ bool SyncJournalDb::updateMetadataTableStructure()
         commitInternal("update database structure: add path index");
     }
 
+    if (1) {
+        SqlQuery query(_db);
+        query.prepare("CREATE INDEX IF NOT EXISTS metadata_parent ON metadata(parent_hash(path));");
+        if (!query.exec()) {
+            sqlFail("updateMetadataTableStructure: create index parent", query);
+            re = false;
+        }
+        commitInternal("update database structure: add parent index");
+    }
+
     if (columns.indexOf("ignoredChildrenRemote") == -1) {
         SqlQuery query(_db);
         query.prepare("ALTER TABLE metadata ADD COLUMN ignoredChildrenRemote INT;");
@@ -847,11 +867,6 @@ QVector<QByteArray> SyncJournalDb::tableColumns(const QByteArray &table)
 qint64 SyncJournalDb::getPHash(const QByteArray &file)
 {
     int64_t h = 0;
-
-    if (file.isEmpty()) {
-        return -1;
-    }
-
     int len = file.length();
 
     h = c_jhash64((uint8_t *)file.data(), len, 0);
@@ -1161,6 +1176,39 @@ bool SyncJournalDb::getFilesBelowPath(const QByteArray &path, const std::functio
     return true;
 }
 
+bool SyncJournalDb::listFilesInPath(const QByteArray& path,
+                                    const std::function<void (const SyncJournalFileRecord &)>& rowCallback)
+{
+    QMutexLocker locker(&_mutex);
+
+    if (_metadataTableIsEmpty)
+        return true;
+
+    if (!checkConnect())
+        return false;
+
+    if (!_listFilesInPathQuery.initOrReset(QByteArrayLiteral(
+            GET_FILE_RECORD_QUERY " WHERE parent_hash(path) = ?1 ORDER BY path||'/' ASC"), _db))
+        return false;
+
+    _listFilesInPathQuery.bindValue(1, getPHash(path));
+
+    if (!_listFilesInPathQuery.exec())
+        return false;
+
+    while (_listFilesInPathQuery.next()) {
+        SyncJournalFileRecord rec;
+        fillFileRecordFromGetQuery(rec, _listFilesInPathQuery);
+        if (!rec._path.startsWith(path) || rec._path.indexOf("/", path.size() + 1) > 0) {
+            qWarning(lcDb) << "hash collision " << path << rec._path;
+            continue;
+        }
+        rowCallback(rec);
+    }
+
+    return true;
+}
+
 int SyncJournalDb::getFileRecordCount()
 {
     QMutexLocker locker(&_mutex);

src/common/syncjournaldb.h

@@ -61,6 +61,7 @@ public:
     bool getFileRecordByInode(quint64 inode, SyncJournalFileRecord *rec);
     bool getFileRecordsByFileId(const QByteArray &fileId, const std::function<void(const SyncJournalFileRecord &)> &rowCallback);
     bool getFilesBelowPath(const QByteArray &path, const std::function<void(const SyncJournalFileRecord&)> &rowCallback);
+    bool listFilesInPath(const QByteArray &path, const std::function<void(const SyncJournalFileRecord&)> &rowCallback);
     bool setFileRecord(const SyncJournalFileRecord &record);
 
     /// Like setFileRecord, but preserves checksums
@@ -276,6 +277,7 @@ private:
     SqlQuery _getFileRecordQueryByFileId;
     SqlQuery _getFilesBelowPathQuery;
     SqlQuery _getAllFilesQuery;
+    SqlQuery _listFilesInPathQuery;
     SqlQuery _setFileRecordQuery;
     SqlQuery _setFileRecordChecksumQuery;
     SqlQuery _setFileRecordLocalMetadataQuery;

src/libsync/discovery.cpp

@@ -98,10 +98,7 @@ void ProcessDirectoryJob::process()
 
     // fetch all the name from the DB
     auto pathU8 = _currentFolder._original.toUtf8();
-    // FIXME do that better (a query that do not get stuff recursively ?)
-    if (!_discoveryData->_statedb->getFilesBelowPath(pathU8, [&](const SyncJournalFileRecord &rec) {
-            if (rec._path.indexOf("/", pathU8.size() + 1) > 0)
-                return;
+    if (!_discoveryData->_statedb->listFilesInPath(pathU8, [&](const SyncJournalFileRecord &rec) {
             auto name = pathU8.isEmpty() ? rec._path : QString::fromUtf8(rec._path.mid(pathU8.size() + 1));
             if (rec._type == ItemTypeVirtualFile || rec._type == ItemTypeVirtualFileDownload) {
                 name.chop(_discoveryData->_syncOptions._virtualFileSuffix.size());