From cfd49c7f0c4f0d1301a068e470125caa526f14de Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 23 Jun 2017 15:50:59 +0200
Subject: [install.php] Add functions for getting and deleting constraints

---
 install.php | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

(limited to 'install.php')

diff --git a/install.php b/install.php
index d09cbff2..da1d5d02 100644
--- a/install.php
+++ b/install.php
@@ -90,6 +90,47 @@ function tableRename($old, $new) {
 }
 
 
+/**
+ * Get all constraints from given table+column to another table+column.
+ *
+ * @param string $table source table, being constrained
+ * @param string $column source column
+ * @param string $refTable referenced table, dictating the constraints
+ * @param string $refColumn referenced column
+ * @return false|string[] list of constraints matching the request, false on error
+ */
+function tableGetContraints($table, $column, $refTable, $refColumn)
+{
+	$db = 'openslx';
+	if (defined('CONFIG_SQL_DB')) {
+		$db = CONFIG_SQL_DB;
+	} elseif (defined('CONFIG_SQL_DSN')) {
+		if (preg_match('/dbname\s*=\s*([^;\s]+)\s*(;|$)/i', CONFIG_SQL_DSN, $out)) {
+			$db = $out[1];
+			define('CONFIG_SQL_DB', $db);
+		}
+	}
+	$res = Database::simpleQuery('SELECT `CONSTRAINT_NAME` FROM information_schema.KEY_COLUMN_USAGE'
+		. ' WHERE `TABLE_SCHEMA` = :db AND `TABLE_NAME` = :table AND `COLUMN_NAME` = :column'
+		. ' AND `REFERENCED_TABLE_NAME` = :refTable AND `REFERENCED_COLUMN_NAME` = :refColumn',
+		compact('db', 'table', 'column', 'refTable', 'refColumn'));
+	if ($res === false)
+		return false;
+	return $res->fetchAll(PDO::FETCH_COLUMN, 0);
+}
+
+/**
+ * Drop constraint from a table.
+ *
+ * @param string $table table name
+ * @param string $constraint constraint name
+ * @return bool success indicator
+ */
+function tableDeleteConstraint($table, $constraint)
+{
+	return Database::exec("ALTER TABLE `$table` DROP FOREIGN KEY `$constraint`") !== false;
+}
+
 function tableCreate($table, $structure, $fatalOnError = true)
 {
 	if (tableExists($table)) {
-- 
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