[stable10] Add index to oc_cards to assist with searching large numbe…

apps/dav/appinfo/Migrations/Version20170519091921.php

@@ -0,0 +1,27 @@
+<?php
+namespace OCA\dav\Migrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use OCP\Migration\ISchemaMigration;
+
+/**
+ * Add index to oc_cards to assist with searching with large numbers of rows
+ */
+class Version20170519091921 implements ISchemaMigration {
+
+	public function changeSchema(Schema $schema, array $options) {
+		$prefix = $options['tablePrefix'];
+		$table = $schema->getTable("${prefix}cards");
+		// Check for existing index spanning these columns
+		foreach ($table->getIndexes() as $index) {
+			// Check if we have a matching index already
+			if(empty(array_diff($index->getColumns(), ['uri', 'addressbookid']))) {
+				return;
+			}
+
+		}
+		// Add the index if we dont have one spanning this column already
+		$table->addIndex(['addressbookid', 'uri'], 'addressbookid_uri_index');
+	}
+
+}