Ensembia/nextcloud-ng_backup
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M5: resumable database dump and faster database restore

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- DbDumper::dumpStep(): tables are dumped until the step's deadline in one
  REPEATABLE READ transaction and resumed at the last primary key in the
  next step; the running table checksum is carried over. A dump that fits
  in one step is fully consistent, otherwise the snapshot records
  dbConsistent=false. BackupService uses it, so the database phase no
  longer needs one long request (hosted Nextcloud, web cron)
- restore inserts 100 rows per statement and leaves tables whose checksum
  already matches the dump untouched
- spike C: 30-step dump gives the same checksums as the one-shot dump;
  restore rewrote only the 3 damaged tables of 147; 300k-row table
  restored in 14.6 s instead of 46 s
This commit is contained in:
Dillard Blom
2026-10-02 11:34:59 +02:00
parent 08b916cac8
commit 56b14a15b0
3 changed files with 154 additions and 55 deletions
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lib/Service/BackupService.php
+18 -8
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@@ -127,14 +127,24 @@ class BackupService {
$state = json_decode($run->getState(), true, 512, JSON_THROW_ON_ERROR);
if ($run->getPhase() === 'db') {
@set_time_limit(0); // the dump is one transaction; it cannot be split across requests yet
$dbStats = [];
$manifest = (new DbDumper($this->db->getInner(), $this->config->getSystemValueString('dbtableprefix', 'oc_')))->dump($repo, $dbStats);
$repo->putObject('db/' . $state['files']['snapshot'], json_encode($manifest, JSON_THROW_ON_ERROR));
$state['files']['meta']['db'] = 'db/' . $state['files']['snapshot'];
$state['dbStats'] = $dbStats + ['tables' => count($manifest['tables']),
'rows' => array_sum(array_column($manifest['tables'], 'rows'))];
$run->setPhase('files');
$dumper = new DbDumper($this->db->getInner(), $this->config->getSystemValueString('dbtableprefix', 'oc_'));
$dbStats = $state['dbStats'] ?? [];
// With system cron the whole dump usually fits in one step (one transaction, fully
// consistent). Under web cron it continues per step; the snapshot then says so.
$dump = $dumper->dumpStep($repo, $state['dump'] ?? $dumper->startDump(), $deadline, $dbStats);
$state['dbStats'] = $dbStats;
if ($dump['done']) {
$manifest = $dumper->manifest($dump);
$repo->putObject('db/' . $state['files']['snapshot'], json_encode($manifest, JSON_THROW_ON_ERROR));
$state['files']['meta']['db'] = 'db/' . $state['files']['snapshot'];
$state['files']['meta']['dbConsistent'] = $manifest['consistent'];
$state['dbStats'] += ['tables' => count($manifest['tables']), 'rows' => array_sum(array_column($manifest['tables'], 'rows')),
'steps' => $dump['steps'], 'consistent' => $manifest['consistent']];
unset($state['dump']);
$run->setPhase('files');
} else {
$state['dump'] = $dump;
}
} else {
$state['files'] = BackupRun::step($repo, $state['files'], $deadline);
if ($state['files']['phase'] === 'done') {