1 files changed, 133 insertions, 0 deletions
diff --git a/lib/private/DB/Adapter.php b/lib/private/DB/Adapter.php
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+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+namespace OC\DB;
+
+use Doctrine\DBAL\Exception;
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+use OC\DB\Exceptions\DbalException;
+
+/**
+ * This handles the way we use to write queries, into something that can be
+ * handled by the database abstraction layer.
+ */
+class Adapter {
+	/**
+	 * @var \OC\DB\Connection $conn
+	 */
+	protected $conn;
+
+	public function __construct($conn) {
+		$this->conn = $conn;
+	}
+
+	/**
+	 * @param string $table name
+	 *
+	 * @return int id of last insert statement
+	 * @throws Exception
+	 */
+	public function lastInsertId($table) {
+		return (int)$this->conn->realLastInsertId($table);
+	}
+
+	/**
+	 * @param string $statement that needs to be changed so the db can handle it
+	 * @return string changed statement
+	 */
+	public function fixupStatement($statement) {
+		return $statement;
+	}
+
+	/**
+	 * Create an exclusive read+write lock on a table
+	 *
+	 * @throws Exception
+	 * @since 9.1.0
+	 */
+	public function lockTable(string $tableName) {
+		$this->conn->beginTransaction();
+		$this->conn->executeUpdate('LOCK TABLE `' . $tableName . '` IN EXCLUSIVE MODE');
+	}
+
+	/**
+	 * Release a previous acquired lock again
+	 *
+	 * @throws Exception
+	 * @since 9.1.0
+	 */
+	public function unlockTable() {
+		$this->conn->commit();
+	}
+
+	/**
+	 * Insert a row if the matching row does not exists. To accomplish proper race condition avoidance
+	 * it is needed that there is also a unique constraint on the values. Then this method will
+	 * catch the exception and return 0.
+	 *
+	 * @param string $table The table name (will replace *PREFIX* with the actual prefix)
+	 * @param array $input data that should be inserted into the table  (column name => value)
+	 * @param array|null $compare List of values that should be checked for "if not exists"
+	 *                            If this is null or an empty array, all keys of $input will be compared
+	 *                            Please note: text fields (clob) must not be used in the compare array
+	 * @return int number of inserted rows
+	 * @throws Exception
+	 * @deprecated 15.0.0 - use unique index and "try { $db->insert() } catch (UniqueConstraintViolationException $e) {}" instead, because it is more reliable and does not have the risk for deadlocks - see https://github.com/nextcloud/server/pull/12371
+	 */
+	public function insertIfNotExist($table, $input, ?array $compare = null) {
+		$compare = $compare ?: array_keys($input);
+
+		// Prepare column names and generate placeholders
+		$columns = '`' . implode('`,`', array_keys($input)) . '`';
+		$placeholders = implode(', ', array_fill(0, count($input), '?'));
+
+		$query = 'INSERT INTO `' . $table . '` (' . $columns . ') '
+			. 'SELECT ' . $placeholders . ' '
+			. 'FROM `' . $table . '` WHERE ';
+
+		$inserts = array_values($input);
+		foreach ($compare as $key) {
+			$query .= '`' . $key . '`';
+			if (is_null($input[$key])) {
+				$query .= ' IS NULL AND ';
+			} else {
+				$inserts[] = $input[$key];
+				$query .= ' = ? AND ';
+			}
+		}
+		$query = substr($query, 0, -5);
+		$query .= ' HAVING COUNT(*) = 0';
+
+		try {
+			return $this->conn->executeUpdate($query, $inserts);
+		} catch (UniqueConstraintViolationException $e) {
+			// This exception indicates a concurrent insert happened between
+			// the insert and the sub-select in the insert, which is safe to ignore.
+			// More details: https://github.com/nextcloud/server/pull/12315
+			return 0;
+		}
+	}
+
+	/**
+	 * @throws \OCP\DB\Exception
+	 */
+	public function insertIgnoreConflict(string $table, array $values) : int {
+		try {
+			$builder = $this->conn->getQueryBuilder();
+			$builder->insert($table);
+			foreach ($values as $key => $value) {
+				$builder->setValue($key, $builder->createNamedParameter($value));
+			}
+			return $builder->executeStatement();
+		} catch (DbalException $e) {
+			if ($e->getReason() === \OCP\DB\Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
+				return 0;
+			}
+			throw $e;
+		}
+	}
+}