Delete poll permanently (#823)

* add logic to irrevocably delete polls

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@uni-tuebingen.de>

* add onDelete fk constraint to tables depending on polls

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@uni-tuebingen.de>

* rename finally/irrevocably to permanently

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@uni-tuebingen.de>

* fix poll still visible after delete and show notification after delete

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@uni-tuebingen.de>

* update migration to delete orphaned entries before adding fk constraint

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@uni-tuebingen.de>

* fix sql syntax for non-pgsql in migration

Signed-off-by: Vinzenz Rosenkranz <vinzenz.rosenkranz@posteo.de>

Co-authored-by: René Gieling <github@dartcafe.de>

1 files changed, 118 insertions, 0 deletions

diff --git a/lib/Migration/Version0104Date20200205104800.php b/lib/Migration/Version0104Date20200205104800.php
new file mode 100644
index 00000000..ecc00280
--- /dev/null
+++ b/lib/Migration/Version0104Date20200205104800.php
@@ -0,0 +1,118 @@
+<?php
+/**
+ * @copyright Copyright (c) 2017 René Gieling <github@dartcafe.de>
+ *
+ * @author René Gieling <github@dartcafe.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as
+ *  published by the Free Software Foundation, either version 3 of the
+ *  License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Polls\Migration;
+
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\Migration\SimpleMigrationStep;
+use OCP\Migration\IOutput;
+
+/**
+ * Installation class for the polls app.
+ * Initial db creation
+ */
+class Version0104Date20200205104800 extends SimpleMigrationStep {
+
+	/** @var IDBConnection */
+	protected $connection;
+
+	/** @var IConfig */
+	protected $config;
+
+    /** @var array */
+    protected $childTables = [
+        'polls_comments',
+        'polls_log',
+        'polls_notif',
+        'polls_options',
+        'polls_share',
+        'polls_votes',
+    ];
+
+	/**
+	 * @param IDBConnection $connection
+	 * @param IConfig $config
+	 */
+	public function __construct(IDBConnection $connection, IConfig $config) {
+		$this->connection = $connection;
+		$this->config = $config;
+	}
+
+
+    /**
+     * @param IOutput $output
+     * @param \Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+     * @param array $options
+     * @return null
+     * @since 13.0.0
+     */
+    public function preSchemaChange(IOutput $output, \Closure $schemaClosure, array $options) {
+        // delete all orphaned entries by selecting all rows
+        // those poll_ids are not present in the polls table
+        //
+        // we have to use a raw query, because NOT EXISTS is not
+        // part of doctrine's expression builder
+        //
+        // get table prefix, as we are running a raw query
+        $prefix = $this->config->getSystemValue('dbtableprefix', 'oc_');
+        // check for orphaned entries in all tables referencing
+        // the main polls table
+        foreach($this->childTables as $tbl) {
+            $child = "$prefix$tbl";
+            $query = "DELETE
+                FROM $child
+                WHERE NOT EXISTS (
+                    SELECT NULL
+                    FROM {$prefix}polls_polls polls
+                    WHERE polls.id = {$child}.poll_id
+                )";
+            $stmt = $this->connection->prepare($query);
+            $stmt->execute();
+        }
+    }
+
+	/**
+	 * @param IOutput $output
+	 * @param \Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 * @since 13.0.0
+	 */
+	public function changeSchema(IOutput $output, \Closure $schemaClosure, array $options) {
+        // add an on delete fk contraint to all tables referencing the main polls table
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+        $eventTable = $schema->getTable('polls_polls');
+        foreach($this->childTables as $tbl) {
+            $table = $schema->getTable($tbl);
+
+            $table->addForeignKeyConstraint($eventTable, ['poll_id'], ['id'], ['onDelete' => 'CASCADE']);
+        }
+
+		return $schema;
+	}
+}