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<?php
declare(strict_types=1);
/**
* SPDX-FileCopyrightText: 2024 Robin Appelman <robin@icewind.nl>
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
namespace OC\DB\QueryBuilder\Sharded;
use OC\DB\ArrayResult;
use OCP\DB\IResult;
use OCP\DB\QueryBuilder\IQueryBuilder;
/**
* Logic for running a query across a number of shards, combining the results
*/
class ShardQueryRunner {
public function __construct(
private ShardConnectionManager $shardConnectionManager,
private ShardDefinition $shardDefinition,
) {
}
/**
* Get the shards for a specific query or null if the shards aren't known in advance
*
* @param bool $allShards
* @param int[] $shardKeys
* @return null|int[]
*/
public function getShards(bool $allShards, array $shardKeys): ?array {
if ($allShards) {
return $this->shardDefinition->getAllShards();
}
$allConfiguredShards = $this->shardDefinition->getAllShards();
if (count($allConfiguredShards) === 1) {
return $allConfiguredShards;
}
if (empty($shardKeys)) {
return null;
}
$shards = array_map(function ($shardKey) {
return $this->shardDefinition->getShardForKey((int)$shardKey);
}, $shardKeys);
return array_values(array_unique($shards));
}
/**
* Try to get the shards that the keys are likely to be in, based on the shard the row was created
*
* @param int[] $primaryKeys
* @return int[]
*/
private function getLikelyShards(array $primaryKeys): array {
$shards = [];
foreach ($primaryKeys as $primaryKey) {
$encodedShard = $primaryKey & ShardDefinition::PRIMARY_KEY_SHARD_MASK;
if ($encodedShard < count($this->shardDefinition->shards) && !in_array($encodedShard, $shards)) {
$shards[] = $encodedShard;
}
}
return $shards;
}
/**
* Execute a SELECT statement across the configured shards
*
* @param IQueryBuilder $query
* @param bool $allShards
* @param int[] $shardKeys
* @param int[] $primaryKeys
* @param array{column: string, order: string}[] $sortList
* @param int|null $limit
* @param int|null $offset
* @return IResult
*/
public function executeQuery(
IQueryBuilder $query,
bool $allShards,
array $shardKeys,
array $primaryKeys,
?array $sortList = null,
?int $limit = null,
?int $offset = null,
): IResult {
$shards = $this->getShards($allShards, $shardKeys);
$results = [];
if ($shards && count($shards) === 1) {
// trivial case
return $query->executeQuery($this->shardConnectionManager->getConnection($this->shardDefinition, $shards[0]));
}
// we have to emulate limit and offset, so we select offset+limit from all shards to ensure we have enough rows
// and then filter them down after we merged the results
if ($limit !== null && $offset !== null) {
$query->setMaxResults($limit + $offset);
}
if ($shards) {
// we know exactly what shards we need to query
foreach ($shards as $shard) {
$shardConnection = $this->shardConnectionManager->getConnection($this->shardDefinition, $shard);
$subResult = $query->executeQuery($shardConnection);
$results = array_merge($results, $subResult->fetchAll());
$subResult->closeCursor();
}
} else {
// we don't know for sure what shards we need to query,
// we first try the shards that are "likely" to have the rows we want, based on the shard that the row was
// originally created in. If we then still haven't found all rows we try the rest of the shards
$likelyShards = $this->getLikelyShards($primaryKeys);
$unlikelyShards = array_diff($this->shardDefinition->getAllShards(), $likelyShards);
$shards = array_merge($likelyShards, $unlikelyShards);
foreach ($shards as $shard) {
$shardConnection = $this->shardConnectionManager->getConnection($this->shardDefinition, $shard);
$subResult = $query->executeQuery($shardConnection);
$rows = $subResult->fetchAll();
$results = array_merge($results, $rows);
$subResult->closeCursor();
if (count($rows) >= count($primaryKeys)) {
// we have all the rows we're looking for
break;
}
}
}
if ($sortList) {
usort($results, function ($a, $b) use ($sortList) {
foreach ($sortList as $sort) {
$valueA = $a[$sort['column']] ?? null;
$valueB = $b[$sort['column']] ?? null;
$cmp = $valueA <=> $valueB;
if ($cmp === 0) {
continue;
}
if ($sort['order'] === 'DESC') {
$cmp = -$cmp;
}
return $cmp;
}
});
}
if ($limit !== null && $offset !== null) {
$results = array_slice($results, $offset, $limit);
} elseif ($limit !== null) {
$results = array_slice($results, 0, $limit);
} elseif ($offset !== null) {
$results = array_slice($results, $offset);
}
return new ArrayResult($results);
}
/**
* Execute an UPDATE or DELETE statement
*
* @param IQueryBuilder $query
* @param bool $allShards
* @param int[] $shardKeys
* @param int[] $primaryKeys
* @return int
* @throws \OCP\DB\Exception
*/
public function executeStatement(IQueryBuilder $query, bool $allShards, array $shardKeys, array $primaryKeys): int {
if ($query->getType() === \Doctrine\DBAL\Query\QueryBuilder::INSERT) {
throw new \Exception('insert queries need special handling');
}
$shards = $this->getShards($allShards, $shardKeys);
$maxCount = count($primaryKeys);
if ($shards && count($shards) === 1) {
return $query->executeStatement($this->shardConnectionManager->getConnection($this->shardDefinition, $shards[0]));
} elseif ($shards) {
$maxCount = PHP_INT_MAX;
} else {
// sort the likely shards before the rest, similar logic to `self::executeQuery`
$likelyShards = $this->getLikelyShards($primaryKeys);
$unlikelyShards = array_diff($this->shardDefinition->getAllShards(), $likelyShards);
$shards = array_merge($likelyShards, $unlikelyShards);
}
$count = 0;
foreach ($shards as $shard) {
$shardConnection = $this->shardConnectionManager->getConnection($this->shardDefinition, $shard);
$count += $query->executeStatement($shardConnection);
if ($count >= $maxCount) {
break;
}
}
return $count;
}
}
|
