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Diffstat (limited to 'lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php')
| -rw-r--r-- | lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php | 462 |
1 files changed, 462 insertions, 0 deletions
diff --git a/lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php b/lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php new file mode 100644 index 00000000000..d748c791321 --- /dev/null +++ b/lib/private/DB/QueryBuilder/Partitioned/PartitionedQueryBuilder.php @@ -0,0 +1,462 @@ +<?php + +declare(strict_types=1); +/** + * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors + * SPDX-License-Identifier: AGPL-3.0-only + */ + +namespace OC\DB\QueryBuilder\Partitioned; + +use OC\DB\QueryBuilder\CompositeExpression; +use OC\DB\QueryBuilder\QuoteHelper; +use OC\DB\QueryBuilder\Sharded\AutoIncrementHandler; +use OC\DB\QueryBuilder\Sharded\ShardConnectionManager; +use OC\DB\QueryBuilder\Sharded\ShardedQueryBuilder; +use OCP\DB\IResult; +use OCP\DB\QueryBuilder\IQueryBuilder; +use OCP\DB\QueryBuilder\IQueryFunction; +use OCP\IDBConnection; + +/** + * A special query builder that automatically splits queries that span across multiple database partitions[1]. + * + * This is done by inspecting the query as it's being built, and when a cross-partition join is detected, + * the part of the query that touches the partition is split of into a different sub-query. + * Then, when the query is executed, the results from the sub-queries are automatically merged. + * + * This whole process is intended to be transparent to any code using the query builder, however it does impose some extra + * limitation for queries that work cross-partition. See the documentation from `InvalidPartitionedQueryException` for more details. + * + * When a join is created in the query, this builder checks if it belongs to the same partition as the table from the + * original FROM/UPDATE/DELETE/INSERT and if not, creates a new "sub query" for the partition. + * Then for every part that is added the query, the part is analyzed to determine which partition the query part is referencing + * and the query part is added to the sub query for that partition. + * + * [1]: A set of tables which can't be queried together with the rest of the tables, such as when sharding is used. + */ +class PartitionedQueryBuilder extends ShardedQueryBuilder { + /** @var array<string, PartitionQuery> $splitQueries */ + private array $splitQueries = []; + /** @var list<PartitionSplit> */ + private array $partitions = []; + + /** @var array{'select': string|array, 'alias': ?string}[] */ + private array $selects = []; + private ?PartitionSplit $mainPartition = null; + private bool $hasPositionalParameter = false; + private QuoteHelper $quoteHelper; + private ?int $limit = null; + private ?int $offset = null; + + public function __construct( + IQueryBuilder $builder, + array $shardDefinitions, + ShardConnectionManager $shardConnectionManager, + AutoIncrementHandler $autoIncrementHandler, + ) { + parent::__construct($builder, $shardDefinitions, $shardConnectionManager, $autoIncrementHandler); + $this->quoteHelper = new QuoteHelper(); + } + + private function newQuery(): IQueryBuilder { + // get a fresh, non-partitioning query builder + $builder = $this->builder->getConnection()->getQueryBuilder(); + if ($builder instanceof PartitionedQueryBuilder) { + $builder = $builder->builder; + } + + return new ShardedQueryBuilder( + $builder, + $this->shardDefinitions, + $this->shardConnectionManager, + $this->autoIncrementHandler, + ); + } + + // we need to save selects until we know all the table aliases + public function select(...$selects) { + if (count($selects) === 1 && is_array($selects[0])) { + $selects = $selects[0]; + } + $this->selects = []; + $this->addSelect(...$selects); + return $this; + } + + public function addSelect(...$select) { + $select = array_map(function ($select) { + return ['select' => $select, 'alias' => null]; + }, $select); + $this->selects = array_merge($this->selects, $select); + return $this; + } + + public function selectAlias($select, $alias) { + $this->selects[] = ['select' => $select, 'alias' => $alias]; + return $this; + } + + /** + * Ensure that a column is being selected by the query + * + * This is mainly used to ensure that the returned rows from both sides of a partition contains the columns of the join predicate + * + * @param string|IQueryFunction $column + * @return void + */ + private function ensureSelect(string|IQueryFunction $column, ?string $alias = null): void { + $checkColumn = $alias ?: $column; + if (str_contains($checkColumn, '.')) { + [$table, $checkColumn] = explode('.', $checkColumn); + $partition = $this->getPartition($table); + } else { + $partition = null; + } + foreach ($this->selects as $select) { + $select = $select['select']; + if (!is_string($select)) { + continue; + } + + if (str_contains($select, '.')) { + [$table, $select] = explode('.', $select); + $selectPartition = $this->getPartition($table); + } else { + $selectPartition = null; + } + if ( + ($select === $checkColumn || $select === '*') + && $selectPartition === $partition + ) { + return; + } + } + if ($alias) { + $this->selectAlias($column, $alias); + } else { + $this->addSelect($column); + } + } + + /** + * Distribute the select statements to the correct partition + * + * This is done at the end instead of when the `select` call is made, because the `select` calls are generally done + * before we know what tables are involved in the query + * + * @return void + */ + private function applySelects(): void { + foreach ($this->selects as $select) { + foreach ($this->partitions as $partition) { + if (is_string($select['select']) && ( + $select['select'] === '*' + || $partition->isColumnInPartition($select['select'])) + ) { + if (isset($this->splitQueries[$partition->name])) { + if ($select['alias']) { + $this->splitQueries[$partition->name]->query->selectAlias($select['select'], $select['alias']); + } else { + $this->splitQueries[$partition->name]->query->addSelect($select['select']); + } + if ($select['select'] !== '*') { + continue 2; + } + } + } + } + + if ($select['alias']) { + parent::selectAlias($select['select'], $select['alias']); + } else { + parent::addSelect($select['select']); + } + } + $this->selects = []; + } + + + public function addPartition(PartitionSplit $partition): void { + $this->partitions[] = $partition; + } + + private function getPartition(string $table): ?PartitionSplit { + foreach ($this->partitions as $partition) { + if ($partition->containsTable($table) || $partition->containsAlias($table)) { + return $partition; + } + } + return null; + } + + public function from($from, $alias = null) { + if (is_string($from) && $partition = $this->getPartition($from)) { + $this->mainPartition = $partition; + if ($alias) { + $this->mainPartition->addAlias($from, $alias); + } + } + return parent::from($from, $alias); + } + + public function innerJoin($fromAlias, $join, $alias, $condition = null): self { + return $this->join($fromAlias, $join, $alias, $condition); + } + + public function leftJoin($fromAlias, $join, $alias, $condition = null): self { + return $this->join($fromAlias, (string)$join, $alias, $condition, PartitionQuery::JOIN_MODE_LEFT); + } + + public function join($fromAlias, $join, $alias, $condition = null, $joinMode = PartitionQuery::JOIN_MODE_INNER): self { + $partition = $this->getPartition($join); + $fromPartition = $this->getPartition($fromAlias); + if ($partition && $partition !== $this->mainPartition) { + // join from the main db to a partition + + $joinCondition = JoinCondition::parse($condition, $join, $alias, $fromAlias); + $partition->addAlias($join, $alias); + + if (!isset($this->splitQueries[$partition->name])) { + $this->splitQueries[$partition->name] = new PartitionQuery( + $this->newQuery(), + $joinCondition->fromAlias ?? $joinCondition->fromColumn, $joinCondition->toAlias ?? $joinCondition->toColumn, + $joinMode + ); + $this->splitQueries[$partition->name]->query->from($join, $alias); + $this->ensureSelect($joinCondition->fromColumn, $joinCondition->fromAlias); + $this->ensureSelect($joinCondition->toColumn, $joinCondition->toAlias); + } else { + $query = $this->splitQueries[$partition->name]->query; + if ($partition->containsAlias($fromAlias)) { + $query->innerJoin($fromAlias, $join, $alias, $condition); + } else { + throw new InvalidPartitionedQueryException("Can't join across partition boundaries more than once"); + } + } + $this->splitQueries[$partition->name]->query->andWhere(...$joinCondition->toConditions); + parent::andWhere(...$joinCondition->fromConditions); + return $this; + } elseif ($fromPartition && $fromPartition !== $partition) { + // join from partition, to the main db + + $joinCondition = JoinCondition::parse($condition, $join, $alias, $fromAlias); + if (str_starts_with($fromPartition->name, 'from_')) { + $partitionName = $fromPartition->name; + } else { + $partitionName = 'from_' . $fromPartition->name; + } + + if (!isset($this->splitQueries[$partitionName])) { + $newPartition = new PartitionSplit($partitionName, [$join]); + $newPartition->addAlias($join, $alias); + $this->partitions[] = $newPartition; + + $this->splitQueries[$partitionName] = new PartitionQuery( + $this->newQuery(), + $joinCondition->fromAlias ?? $joinCondition->fromColumn, $joinCondition->toAlias ?? $joinCondition->toColumn, + $joinMode + ); + $this->ensureSelect($joinCondition->fromColumn, $joinCondition->fromAlias); + $this->ensureSelect($joinCondition->toColumn, $joinCondition->toAlias); + $this->splitQueries[$partitionName]->query->from($join, $alias); + $this->splitQueries[$partitionName]->query->andWhere(...$joinCondition->toConditions); + parent::andWhere(...$joinCondition->fromConditions); + } else { + $fromPartition->addTable($join); + $fromPartition->addAlias($join, $alias); + + $query = $this->splitQueries[$partitionName]->query; + $query->innerJoin($fromAlias, $join, $alias, $condition); + } + return $this; + } else { + // join within the main db or a partition + if ($joinMode === PartitionQuery::JOIN_MODE_INNER) { + return parent::innerJoin($fromAlias, $join, $alias, $condition); + } elseif ($joinMode === PartitionQuery::JOIN_MODE_LEFT) { + return parent::leftJoin($fromAlias, $join, $alias, $condition); + } elseif ($joinMode === PartitionQuery::JOIN_MODE_RIGHT) { + return parent::rightJoin($fromAlias, $join, $alias, $condition); + } else { + throw new \InvalidArgumentException("Invalid join mode: $joinMode"); + } + } + } + + /** + * Flatten a list of predicates by merging the parts of any "AND" expression into the list of predicates + * + * @param array $predicates + * @return array + */ + private function flattenPredicates(array $predicates): array { + $result = []; + foreach ($predicates as $predicate) { + if ($predicate instanceof CompositeExpression && $predicate->getType() === CompositeExpression::TYPE_AND) { + $result = array_merge($result, $this->flattenPredicates($predicate->getParts())); + } else { + $result[] = $predicate; + } + } + return $result; + } + + /** + * Split an array of predicates (WHERE query parts) by the partition they reference + * + * @param array $predicates + * @return array<string, array> + */ + private function splitPredicatesByParts(array $predicates): array { + $predicates = $this->flattenPredicates($predicates); + + $partitionPredicates = []; + foreach ($predicates as $predicate) { + $partition = $this->getPartitionForPredicate((string)$predicate); + if ($this->mainPartition === $partition) { + $partitionPredicates[''][] = $predicate; + } elseif ($partition) { + $partitionPredicates[$partition->name][] = $predicate; + } else { + $partitionPredicates[''][] = $predicate; + } + } + return $partitionPredicates; + } + + public function where(...$predicates) { + return $this->andWhere(...$predicates); + } + + public function andWhere(...$where) { + if ($where) { + foreach ($this->splitPredicatesByParts($where) as $alias => $predicates) { + if (isset($this->splitQueries[$alias])) { + // when there is a condition on a table being left-joined it starts to behave as if it's an inner join + // since any joined column that doesn't have the left part will not match the condition + // when there the condition is `$joinToColumn IS NULL` we instead mark the query as excluding the left half + if ($this->splitQueries[$alias]->joinMode === PartitionQuery::JOIN_MODE_LEFT) { + $this->splitQueries[$alias]->joinMode = PartitionQuery::JOIN_MODE_INNER; + + $column = $this->quoteHelper->quoteColumnName($this->splitQueries[$alias]->joinToColumn); + foreach ($predicates as $predicate) { + if ((string)$predicate === "$column IS NULL") { + $this->splitQueries[$alias]->joinMode = PartitionQuery::JOIN_MODE_LEFT_NULL; + } else { + $this->splitQueries[$alias]->query->andWhere($predicate); + } + } + } else { + $this->splitQueries[$alias]->query->andWhere(...$predicates); + } + } else { + parent::andWhere(...$predicates); + } + } + } + return $this; + } + + + private function getPartitionForPredicate(string $predicate): ?PartitionSplit { + foreach ($this->partitions as $partition) { + + if (str_contains($predicate, '?')) { + $this->hasPositionalParameter = true; + } + if ($partition->checkPredicateForTable($predicate)) { + return $partition; + } + } + return null; + } + + public function update($update = null, $alias = null) { + return parent::update($update, $alias); + } + + public function insert($insert = null) { + return parent::insert($insert); + } + + public function delete($delete = null, $alias = null) { + return parent::delete($delete, $alias); + } + + public function setMaxResults($maxResults) { + if ($maxResults > 0) { + $this->limit = (int)$maxResults; + } + return parent::setMaxResults($maxResults); + } + + public function setFirstResult($firstResult) { + if ($firstResult > 0) { + $this->offset = (int)$firstResult; + } + return parent::setFirstResult($firstResult); + } + + public function executeQuery(?IDBConnection $connection = null): IResult { + $this->applySelects(); + if ($this->splitQueries && $this->hasPositionalParameter) { + throw new InvalidPartitionedQueryException("Partitioned queries aren't allowed to to positional arguments"); + } + foreach ($this->splitQueries as $split) { + $split->query->setParameters($this->getParameters(), $this->getParameterTypes()); + } + if (count($this->splitQueries) > 0) { + $hasNonLeftJoins = array_reduce($this->splitQueries, function (bool $hasNonLeftJoins, PartitionQuery $query) { + return $hasNonLeftJoins || $query->joinMode !== PartitionQuery::JOIN_MODE_LEFT; + }, false); + if ($hasNonLeftJoins) { + if (is_int($this->limit)) { + throw new InvalidPartitionedQueryException('Limit is not allowed in partitioned queries'); + } + if (is_int($this->offset)) { + throw new InvalidPartitionedQueryException('Offset is not allowed in partitioned queries'); + } + } + } + + $s = $this->getSQL(); + $result = parent::executeQuery($connection); + if (count($this->splitQueries) > 0) { + return new PartitionedResult($this->splitQueries, $result); + } else { + return $result; + } + } + + public function executeStatement(?IDBConnection $connection = null): int { + if (count($this->splitQueries)) { + throw new InvalidPartitionedQueryException("Partitioning write queries isn't supported"); + } + return parent::executeStatement($connection); + } + + public function getSQL() { + $this->applySelects(); + return parent::getSQL(); + } + + public function getPartitionCount(): int { + return count($this->splitQueries) + 1; + } + + public function hintShardKey(string $column, mixed $value, bool $overwrite = false): self { + if (str_contains($column, '.')) { + [$alias, $column] = explode('.', $column); + $partition = $this->getPartition($alias); + if ($partition) { + $this->splitQueries[$partition->name]->query->hintShardKey($column, $value, $overwrite); + } else { + parent::hintShardKey($column, $value, $overwrite); + } + } else { + parent::hintShardKey($column, $value, $overwrite); + } + return $this; + } +} |