1 files changed, 75 insertions, 0 deletions
diff --git a/lib/private/DB/QueryBuilder/Partitioned/PartitionQuery.php b/lib/private/DB/QueryBuilder/Partitioned/PartitionQuery.php
new file mode 100644
index 00000000000..a5024b478d3
--- /dev/null
+++ b/lib/private/DB/QueryBuilder/Partitioned/PartitionQuery.php
@@ -0,0 +1,75 @@
+<?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 OCP\DB\QueryBuilder\IQueryBuilder;
+
+/**
+ * A sub-query from a partitioned join
+ */
+class PartitionQuery {
+	public const JOIN_MODE_INNER = 'inner';
+	public const JOIN_MODE_LEFT = 'left';
+	// left-join where the left side IS NULL
+	public const JOIN_MODE_LEFT_NULL = 'left_null';
+
+	public const JOIN_MODE_RIGHT = 'right';
+
+	public function __construct(
+		public IQueryBuilder $query,
+		public string $joinFromColumn,
+		public string $joinToColumn,
+		public string $joinMode,
+	) {
+		if ($joinMode !== self::JOIN_MODE_LEFT && $joinMode !== self::JOIN_MODE_INNER) {
+			throw new InvalidPartitionedQueryException("$joinMode joins aren't allowed in partitioned queries");
+		}
+	}
+
+	public function mergeWith(array $rows): array {
+		if (empty($rows)) {
+			return [];
+		}
+		// strip table/alias from column names
+		$joinFromColumn = preg_replace('/\w+\./', '', $this->joinFromColumn);
+		$joinToColumn = preg_replace('/\w+\./', '', $this->joinToColumn);
+
+		$joinFromValues = array_map(function (array $row) use ($joinFromColumn) {
+			return $row[$joinFromColumn];
+		}, $rows);
+		$joinFromValues = array_filter($joinFromValues, function ($value) {
+			return $value !== null;
+		});
+		$this->query->andWhere($this->query->expr()->in($this->joinToColumn, $this->query->createNamedParameter($joinFromValues, IQueryBuilder::PARAM_STR_ARRAY, ':' . uniqid())));
+
+		$s = $this->query->getSQL();
+		$partitionedRows = $this->query->executeQuery()->fetchAll();
+
+		$columns = $this->query->getOutputColumns();
+		$nullResult = array_combine($columns, array_fill(0, count($columns), null));
+
+		$partitionedRowsByKey = [];
+		foreach ($partitionedRows as $partitionedRow) {
+			$partitionedRowsByKey[$partitionedRow[$joinToColumn]][] = $partitionedRow;
+		}
+		$result = [];
+		foreach ($rows as $row) {
+			if (isset($partitionedRowsByKey[$row[$joinFromColumn]])) {
+				if ($this->joinMode !== self::JOIN_MODE_LEFT_NULL) {
+					foreach ($partitionedRowsByKey[$row[$joinFromColumn]] as $partitionedRow) {
+						$result[] = array_merge($row, $partitionedRow);
+					}
+				}
+			} elseif ($this->joinMode === self::JOIN_MODE_LEFT || $this->joinMode === self::JOIN_MODE_LEFT_NULL) {
+				$result[] = array_merge($nullResult, $row);
+			}
+		}
+		return $result;
+	}
+}