fix: keep writes transactional after MySQL deadlock 1213

system/Database/BaseConnection.php

@@ -337,6 +337,20 @@ abstract class BaseConnection implements ConnectionInterface
      */
     protected $transFailure = false;
 
+    /**
+     * The server has already rolled this transaction back (MySQLi errno 1213).
+     * mysqli::commit() still returns true, so transCommit() must not report success.
+     */
+    protected bool $transServerRolledBack = false;
+
+    /**
+     * The next statement must open a server transaction before it runs.
+     * InnoDB ended the previous one and the connection is back in autocommit.
+     * Errno 1205 does not set this: innodb_rollback_on_timeout decides whether
+     * that error rolled the transaction back.
+     */
+    protected bool $transNeedsServerRestart = false;
+
     /**
      * Whether to throw exceptions during transaction
      */
@@ -1022,6 +1036,7 @@ public function transBegin(bool $testMode = false): bool
 
         if ($this->_transBegin()) {
             $this->transDepth++;
+            $this->clearServerRolledBackTransaction();
 
             return true;
         }
@@ -1039,7 +1054,24 @@ public function transCommit(): bool
         }
 
         // When transactions are nested we only begin/commit/rollback the outermost ones
-        if ($this->transDepth > 1 || $this->_transCommit()) {
+        if ($this->transDepth > 1) {
+            $this->transDepth--;
+
+            return true;
+        }
+
+        // InnoDB already removed the victim transaction. mysqli::commit()
+        // returns true anyway, which would publish later writes and report success.
+        // Roll back the restarted server transaction so a false return ends the
+        // transaction, as transComplete() does. Otherwise a caller that retries
+        // without transRollback() nests inside it and nothing commits.
+        if ($this->transServerRolledBack) {
+            $this->transRollback();
+
+            return false;
+        }
+
+        if ($this->_transCommit()) {
             $this->transDepth--;
 
             return true;
@@ -1061,6 +1093,10 @@ public function transRollback(): bool
         if ($this->transDepth > 1 || $this->_transRollback()) {
             $this->transDepth--;
 
+            if ($this->transDepth === 0) {
+                $this->clearServerRolledBackTransaction();
+            }
+
             return true;
         }
 
@@ -1089,6 +1125,37 @@ public function handleTransStatus(): void
         }
     }
 
+    /**
+     * Remember that the server has rolled the open transaction back.
+     */
+    protected function markServerRolledBackTransaction(): void
+    {
+        $this->transServerRolledBack   = true;
+        $this->transNeedsServerRestart = true;
+    }
+
+    /**
+     * True while the next statement must BEGIN before it runs.
+     */
+    protected function serverTransactionRestartPending(): bool
+    {
+        return $this->transNeedsServerRestart && $this->transDepth > 0;
+    }
+
+    /**
+     * BEGIN succeeded. Clear the restart only now, so a failed BEGIN keeps it pending.
+     */
+    protected function serverTransactionRestarted(): void
+    {
+        $this->transNeedsServerRestart = false;
+    }
+
+    private function clearServerRolledBackTransaction(): void
+    {
+        $this->transServerRolledBack   = false;
+        $this->transNeedsServerRestart = false;
+    }
+
     /**
      * Begin Transaction
      */

system/Database/MySQLi/Connection.php

@@ -291,6 +291,16 @@ protected function execute(string $sql)
         }
 
         try {
+            // Errno 1213 ends the server transaction. Begin again before this
+            // statement so it does not autocommit. A failed BEGIN goes through
+            // the normal error path below, and the restart stays pending.
+            // Errno 1205 is not handled: innodb_rollback_on_timeout decides
+            // whether InnoDB rolled that transaction back.
+            if ($this->connID instanceof mysqli && $this->serverTransactionRestartPending()) {
+                $this->connID->begin_transaction();
+                $this->serverTransactionRestarted();
+            }
+
             return $this->connID->query($this->prepQuery($sql), $this->resultMode);
         } catch (mysqli_sql_exception $e) {
             log_message('error', "{message}\nin {exFile} on line {exLine}.\n{trace}", [
@@ -300,6 +310,10 @@ protected function execute(string $sql)
                 'trace'   => render_backtrace($e->getTrace()),
             ]);
 
+            if ($e->getCode() === 1213 && $this->transDepth > 0) {
+                $this->markServerRolledBackTransaction();
+            }
+
             if ($this->DBDebug) {
                 throw new DatabaseException($e->getMessage(), $e->getCode(), $e);
             }