From 5826d219772ffaccd62a9177af044edb81ac41b6 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Wed, 6 Mar 2019 17:29:38 +0100
Subject: install.php: Resolve conflicts before adding constraint

---
 install.php | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'install.php')

diff --git a/install.php b/install.php
index c471f4b6..47084528 100644
--- a/install.php
+++ b/install.php
@@ -180,6 +180,19 @@ function tableAddConstraint($table, $column, $refTable, $refColumn, $actions, $i
 		// Kill the old one
 		$ret = tableDeleteConstraint($table, $test['CONSTRAINT_NAME']);
 	}
+	if ($delete === 'CASCADE') {
+		// Deletes are cascaded, so make sure first that all rows get purged that would
+		// violate the constraint
+		Database::exec("DELETE `$table` FROM `$table`
+				LEFT JOIN `$refTable` ON (`$table`.`$column` = `$refTable`.`$refColumn`)
+				WHERE `$refTable`.`$refColumn` IS NULL");
+	} elseif ($delete === 'SET NULL') {
+		// Similar to above; SET NULL constraint, so do that for violating entries
+		Database::exec("UPDATE `$table`
+				LEFT JOIN `$refTable` ON (`$table`.`$column` = `$refTable`.`$refColumn`)
+				SET `$table`.`$column` = NULL
+				WHERE `$refTable`.`$refColumn` IS NULL");
+	}
 	// Need to create
 	$ret = Database::exec("ALTER TABLE `$table` ADD CONSTRAINT FOREIGN KEY (`$column`)
 			REFERENCES `$refTable` (`$refColumn`)
@@ -188,7 +201,7 @@ function tableAddConstraint($table, $column, $refTable, $refColumn, $actions, $i
 		if ($ignoreError) {
 			return UPDATE_FAILED;
 		} else {
-			finalResponse(UPDATE_FAILED, 'DB: Cannot add constraint: ' . Database::lastError());
+			finalResponse(UPDATE_FAILED, "Cannot add constraint $table.$column -> $refTable.$refColumn: " . Database::lastError());
 		}
 	}
 	return UPDATE_DONE;
-- 
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