dillard
48bb829d45
- 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
369 lines
15 KiB
PHP
369 lines
15 KiB
PHP
<?php
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declare(strict_types=1);
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// SPDX-FileCopyrightText: 2026 Dillard Blom
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// SPDX-License-Identifier: AGPL-3.0-or-later
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namespace OCA\NgBackup\Db;
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use Doctrine\DBAL\Connection;
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use Doctrine\DBAL\TransactionIsolationLevel;
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use Doctrine\DBAL\Types\BinaryType;
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use Doctrine\DBAL\Types\BlobType;
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use OCA\NgBackup\Repository\Repository;
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/**
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* Logical database dump and restore through the Nextcloud database connection: no pg_dump,
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* mysqldump or extra PHP extensions.
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*
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* - All tables with the Nextcloud prefix are dumped inside one REPEATABLE READ, read-only
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* transaction, so the dump is consistent without maintenance mode.
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* - Rows are read in primary-key order with keyset pagination (pdo_pgsql buffers whole result
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* sets, so a single big SELECT would not stream).
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* - Each table becomes its own blob stream of JSON lines: a header line, then one JSON array per
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* row. A table that did not change produces the same blobs and costs nothing in the next run.
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* - The schema itself is not dumped: it comes from Nextcloud's migrations on the instance that is
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* restored into (same Nextcloud and app versions). The dump records those versions.
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*
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* Phase 0 uses the Doctrine connection behind IDBConnection (private API) for schema
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* introspection; to be replaced by information_schema queries or a public API.
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*/
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final class DbDumper {
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private const BATCH = 2000;
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/** Rows per INSERT on restore; keeps the number of bound parameters well below database limits. */
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private const INSERT_ROWS = 100;
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/** Tables without a primary key are read in one query; refuse that above this size. */
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private const MAX_ROWS_WITHOUT_PK = 50000;
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public function __construct(
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private Connection $db,
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private string $prefix,
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) {
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}
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/**
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* Dump everything in one go (one transaction, fully consistent).
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*
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* @return array{tables: array<string, array{blobs: list<string>, rows: int, bytes: int, sha256: string}>, sequences: array, provider: string, consistent: bool}
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*/
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public function dump(Repository $repo, array &$stats): array {
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$state = $this->startDump();
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while (!$state['done']) {
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$state = $this->dumpStep($repo, $state, PHP_FLOAT_MAX, $stats);
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}
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return $this->manifest($state);
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}
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/** State for a resumable dump (see dumpStep()). */
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public function startDump(): array {
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$tables = array_values(array_filter($this->db->createSchemaManager()->listTableNames(), fn (string $t) => str_starts_with($t, $this->prefix)));
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sort($tables);
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return ['tables' => $tables, 'i' => 0, 'after' => null, 'segments' => [], 'rows' => 0, 'bytes' => 0, 'hash' => null,
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'result' => [], 'sequences' => [], 'steps' => 0, 'done' => false];
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}
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/**
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* Dump tables until $deadline, inside one REPEATABLE READ transaction for this step. A table
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* that does not fit is resumed in the next step at the last primary key written. If the whole
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* dump fits in one step it is fully consistent; otherwise each step is consistent on its own
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* ('consistent' => false in the manifest).
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*/
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public function dumpStep(Repository $repo, array $state, float $deadline, array &$stats): array {
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$state['steps']++;
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$sm = $this->db->createSchemaManager();
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$this->db->setTransactionIsolation(TransactionIsolationLevel::REPEATABLE_READ);
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$this->db->beginTransaction();
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try {
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if ($this->db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
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$this->db->executeStatement('SET TRANSACTION READ ONLY');
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}
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while ($state['i'] < count($state['tables'])) {
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$table = $state['tables'][$state['i']];
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$schema = $sm->introspectTable($table);
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$writer = $repo->blobWriter($stats);
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$hash = $state['hash'] !== null ? unserialize(base64_decode($state['hash']), ['allowed_classes' => [\HashContext::class]]) : hash_init('sha256');
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if ($state['after'] === null && $state['segments'] === []) {
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$writer->write($this->header($schema) . "\n");
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}
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$complete = true;
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foreach ($this->rowLines($schema, $state['after']) as [$key, $line]) {
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$writer->write($line . "\n");
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hash_update($hash, $line . "\n");
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$state['rows']++;
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$state['after'] = $key;
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if (microtime(true) >= $deadline) {
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$complete = false;
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break;
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}
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}
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$state['segments'][] = $writer->finish();
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$state['bytes'] += $writer->bytes();
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if (!$complete) {
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$state['hash'] = base64_encode(serialize($hash));
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break;
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}
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$state['result'][$table] = ['blobs' => array_merge(...$state['segments']), 'rows' => $state['rows'],
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'bytes' => $state['bytes'], 'sha256' => hash_final($hash)];
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$state = array_merge($state, ['i' => $state['i'] + 1, 'after' => null, 'segments' => [], 'rows' => 0, 'bytes' => 0, 'hash' => null]);
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if (microtime(true) >= $deadline && $state['i'] < count($state['tables'])) {
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break;
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}
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}
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if ($state['i'] >= count($state['tables'])) {
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$state['sequences'] = $this->sequenceStates($state['tables']);
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$state['done'] = true;
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}
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} finally {
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$this->db->rollBack();
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}
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$repo->flushPacks();
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return $state;
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}
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public function manifest(array $state): array {
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return ['tables' => $state['result'], 'sequences' => $state['sequences'],
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'provider' => get_class($this->db->getDatabasePlatform()), 'consistent' => $state['steps'] === 1];
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}
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/**
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* Replace the contents of every table in the dump. Tables that exist but are not in the dump
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* are left alone (e.g. a newer app); the caller decides whether that is acceptable.
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*
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* @param array{tables: array<string, array{blobs: list<string>, rows: int}>} $manifest
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*/
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public function restore(Repository $repo, array $manifest, ?array &$report = null): int {
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$sm = $this->db->createSchemaManager();
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$existing = array_flip($sm->listTableNames());
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$total = 0;
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$report = ['skipped' => [], 'restored' => []];
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$this->db->beginTransaction();
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try {
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foreach ($manifest['tables'] as $table => $info) {
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if (!isset($existing[$table])) {
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throw new \RuntimeException("Table $table from the backup does not exist here (different app versions?)");
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}
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// Unchanged since the backup: leave it alone (much faster than delete + insert).
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$live = $this->checksum($table);
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if ($live['rows'] === $info['rows'] && hash_equals($info['sha256'], $live['sha256'])) {
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$report['skipped'][] = $table;
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continue;
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}
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$this->db->executeStatement('DELETE FROM ' . $this->db->quoteIdentifier($table));
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$columns = null;
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$binary = [];
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$batch = [];
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foreach ($repo->readLines($info['blobs']) as $line) {
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if ($line === '') {
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continue;
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}
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$data = json_decode($line, true, 512, JSON_THROW_ON_ERROR);
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if ($columns === null) {
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$columns = $data['columns'];
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$binary = array_flip($data['binary']);
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continue;
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}
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$row = [];
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foreach ($columns as $i => $col) {
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$value = $data[$i];
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if (is_array($value) && isset($value['$b'])) {
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$value = base64_decode($value['$b'], true); // text that was not valid UTF-8
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}
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$row[] = ($value !== null && isset($binary[$col])) ? base64_decode($value, true) : $value;
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}
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$batch[] = $row;
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if (count($batch) >= self::INSERT_ROWS) {
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$total += $this->insertBatch($table, $columns, $batch, $binary);
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$batch = [];
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}
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}
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if ($batch !== []) {
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$total += $this->insertBatch($table, $columns, $batch, $binary);
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}
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$report['restored'][] = $table;
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}
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$this->restoreSequences($manifest['sequences'] ?? []);
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$this->db->commit();
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} catch (\Throwable $e) {
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$this->db->rollBack();
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throw $e;
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}
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return $total;
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}
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/** Same checksum as dump(): sha256 over the row lines in primary-key order. */
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public function checksum(string $table): array {
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$hash = hash_init('sha256');
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$rows = 0;
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foreach ($this->rowLines($this->db->createSchemaManager()->introspectTable($table)) as [, $line]) {
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hash_update($hash, $line . "\n");
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$rows++;
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}
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return ['rows' => $rows, 'sha256' => hash_final($hash)];
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}
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private function header(\Doctrine\DBAL\Schema\Table $table): string {
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[$columns, $binary, $pk] = $this->describe($table);
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return json_encode(['table' => $table->getName(), 'columns' => $columns, 'binary' => $binary, 'pk' => $pk], JSON_THROW_ON_ERROR);
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}
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/** @return array{0: list<string>, 1: list<string>, 2: list<string>} columns, binary columns, primary key */
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private function describe(\Doctrine\DBAL\Schema\Table $table): array {
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$columns = array_values(array_map(fn ($c) => $c->getName(), $table->getColumns()));
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$binary = [];
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foreach ($table->getColumns() as $c) {
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if ($c->getType() instanceof BlobType || $c->getType() instanceof BinaryType) {
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$binary[] = $c->getName();
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}
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}
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return [$columns, $binary, $table->getPrimaryKey()?->getColumns() ?? []];
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}
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/**
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* Rows in primary-key order, after the key $after (resume), as [key, JSON line].
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*
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* @return \Generator<array{0: list<mixed>|null, 1: string}>
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*/
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private function rowLines(\Doctrine\DBAL\Schema\Table $table, ?array $after = null): \Generator {
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[$columns, $binary, $pk] = $this->describe($table);
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$binaryFlip = array_flip($binary);
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$q = fn (string $c) => $this->db->quoteIdentifier($c);
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$select = 'SELECT ' . implode(', ', array_map($q, $columns)) . ' FROM ' . $q($table->getName());
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if ($pk === []) {
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// Nextcloud requires primary keys; small odd tables are read in one query (not resumable).
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$count = (int)$this->db->fetchOne('SELECT COUNT(*) FROM ' . $q($table->getName()));
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if ($count > self::MAX_ROWS_WITHOUT_PK) {
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throw new \RuntimeException("Table {$table->getName()} has no primary key and $count rows; cannot dump it with bounded memory");
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}
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$batches = [$this->db->fetchAllNumeric($select)];
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$pkIdx = [];
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} else {
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$batches = $this->keysetBatches($select, $pk, $columns, $after);
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$pkIdx = array_map(fn ($c) => array_search($c, $columns, true), $pk);
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}
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foreach ($batches as $rows) {
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foreach ($rows as $row) {
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$key = $pkIdx === [] ? null : array_map(fn ($i) => $row[$i], $pkIdx);
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foreach ($columns as $i => $col) {
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if (is_resource($row[$i])) {
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$row[$i] = stream_get_contents($row[$i]);
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}
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if ($row[$i] !== null && isset($binaryFlip[$col])) {
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$row[$i] = base64_encode((string)$row[$i]);
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} elseif (is_string($row[$i]) && !mb_check_encoding($row[$i], 'UTF-8')) {
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// Keep invalid UTF-8 byte-exact instead of substituting characters.
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$row[$i] = ['$b' => base64_encode($row[$i])];
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} elseif (is_int($row[$i]) || is_float($row[$i]) || is_bool($row[$i])) {
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// Normalise: drivers differ in returning numbers as int or string.
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$row[$i] = (string)(is_bool($row[$i]) ? (int)$row[$i] : $row[$i]);
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}
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}
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yield [$key, json_encode($row, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_THROW_ON_ERROR)];
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}
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}
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}
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/** @return \Generator<list<list<mixed>>> */
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private function keysetBatches(string $select, array $pk, array $columns, ?array $after): \Generator {
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$q = fn (string $c) => $this->db->quoteIdentifier($c);
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$order = ' ORDER BY ' . implode(', ', array_map($q, $pk));
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$cols = array_map(fn ($c) => $q($c), $pk);
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$last = $after;
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while (true) {
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$sql = $select;
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$params = [];
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if ($last !== null) {
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// Row-value comparison (a, b) > (?, ?), supported by PostgreSQL, MySQL/MariaDB and SQLite.
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$sql .= ' WHERE (' . implode(', ', $cols) . ') > (' . implode(', ', array_fill(0, count($pk), '?')) . ')';
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$params = $last;
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}
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$rows = $this->db->fetchAllNumeric($sql . $order . ' LIMIT ' . self::BATCH, $params);
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if ($rows === []) {
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return;
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}
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yield $rows;
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if (count($rows) < self::BATCH) {
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return;
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}
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$end = end($rows);
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$last = array_map(fn ($c) => $end[array_search($c, $columns, true)], $pk);
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}
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}
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/** One INSERT with several rows (portable multi-row VALUES). */
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private function insertBatch(string $table, array $columns, array $rows, array $binary): int {
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$q = fn (string $c) => $this->db->quoteIdentifier($c);
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$placeholders = '(' . implode(', ', array_fill(0, count($columns), '?')) . ')';
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$sql = 'INSERT INTO ' . $q($table) . ' (' . implode(', ', array_map($q, $columns)) . ') VALUES '
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. implode(', ', array_fill(0, count($rows), $placeholders));
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$params = [];
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$types = [];
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foreach ($rows as $row) {
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foreach ($columns as $i => $col) {
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$params[] = $row[$i];
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$types[] = isset($binary[$col]) ? \Doctrine\DBAL\ParameterType::LARGE_OBJECT : ($row[$i] === null ? \Doctrine\DBAL\ParameterType::NULL : \Doctrine\DBAL\ParameterType::STRING);
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}
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}
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$this->db->executeStatement($sql, $params, $types);
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return count($rows);
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}
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/**
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* Exact state of every sequence owned by a dumped column (PostgreSQL), so a restore continues
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* where the original left off, not at MAX(id)+1.
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*
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* @return array<string, array{table:string, column:string, last:int|null, called:bool}>
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*/
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private function sequenceStates(array $tables): array {
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if (!$this->db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
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return []; // MySQL/SQLite derive AUTO_INCREMENT from the data
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}
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$rows = $this->db->fetchAllAssociative(
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"SELECT c.table_name, c.column_name, pg_get_serial_sequence(quote_ident(c.table_name), c.column_name) AS seq
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FROM information_schema.columns c
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WHERE c.table_schema = current_schema() AND pg_get_serial_sequence(quote_ident(c.table_name), c.column_name) IS NOT NULL");
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$wanted = array_flip($tables);
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$result = [];
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foreach ($rows as $r) {
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if (!isset($wanted[$r['table_name']])) {
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continue;
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}
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$state = $this->db->fetchAssociative('SELECT last_value, is_called FROM ' . self::sequenceIdentifier($r['seq']));
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$result[$r['seq']] = ['table' => $r['table_name'], 'column' => $r['column_name'],
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// A never-used sequence reports last_value = start value with is_called = false.
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'last' => $state ? (int)$state['last_value'] : null,
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'called' => (bool)($state['is_called'] ?? false)];
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}
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return $result;
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}
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/** pg_get_serial_sequence() returns a catalog name like public.oc_x_id_seq or "My"."seq"; refuse anything else. */
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private static function sequenceIdentifier(string $name): string {
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if (!preg_match('/^("[^"]+"|[a-z_][a-z0-9_$]*)\.("[^"]+"|[a-z_][a-z0-9_$]*)$/i', $name)) {
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throw new \RuntimeException('Unexpected sequence name: ' . $name);
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}
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return $name;
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}
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private function restoreSequences(array $sequences): void {
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if (!$this->db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
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return;
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}
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foreach ($sequences as $info) {
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$seq = $this->db->fetchOne('SELECT pg_get_serial_sequence(quote_ident(?), ?)', [$info['table'], $info['column']]);
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if ($seq === false || $seq === null) {
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continue;
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}
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if ($info['last'] === null) {
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// Never used: start at 1 (or after the data, if rows were inserted with explicit ids).
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$max = (int)$this->db->fetchOne(sprintf('SELECT COALESCE(MAX(%s), 0) FROM %s',
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$this->db->quoteIdentifier($info['column']), $this->db->quoteIdentifier($info['table'])));
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$this->db->executeQuery('SELECT setval(CAST(? AS regclass), ?, false)', [$seq, $max + 1]);
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} else {
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$this->db->executeQuery('SELECT setval(CAST(? AS regclass), ?, ?)', [$seq, $info['last'], $info['called']],
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[\Doctrine\DBAL\ParameterType::STRING, \Doctrine\DBAL\ParameterType::INTEGER, \Doctrine\DBAL\ParameterType::BOOLEAN]);
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}
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}
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}
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}
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