fix: Add indexes on receiver and node

Signed-off-by: Enjeck C. <patrathewhiz@gmail.com>

lib/Migration/Version000900Date20250710000000.php

@@ -0,0 +1,63 @@
+<?php
+
+/** @noinspection PhpUnused */
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCA\Tables\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/**
+ * Migration that adds performance indexes to the tables_shares table
+ *
+ * These indexes optimize the following query patterns:
+ * 1. Filtering by node_id and node_type - prioritizing high selectivity columns first
+ * 2. Filtering by receiver and receiver_type - prioritizing high selectivity columns first
+ * 3. Covering index for the common lookup pattern used in findAllSharesForNodeTo
+ *
+ * Index Selectivity Considerations:
+ * - High selectivity columns (many unique values): node_id, receiver
+ * - Low selectivity columns (few unique values): node_type, receiver_type
+ * - The first two indexes prioritize high selectivity columns first for better performance
+ * - The third is a covering index that matches the exact query pattern used in the code
+ *
+ * This significantly improves performance for:
+ * - Looking up shares for a specific node
+ * - Finding shares for a specific user/group/circle
+ * - The optimized findAllSharesForNodeTo query that fetches all shares in one operation
+ */
+
+class Version000900Date20250710000000 extends SimpleMigrationStep {
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		$tableName = 'tables_shares';
+
+		if ($schema->hasTable($tableName)) {
+			$table = $schema->getTable($tableName);
+
+			if (!$table->hasIndex('shares_node_idx')) {
+				$table->addIndex(['node_id', 'node_type'], 'shares_node_idx');
+			}
+
+			if (!$table->hasIndex('shares_receiver_idx')) {
+				$table->addIndex(['receiver', 'receiver_type'], 'shares_receiver_idx');
+			}
+		}
+
+		return $schema;
+	}
+}