Update FieldtypeMulti::savePageField to use InnoDB transactions when possible, plus add a new shortcut method: WireDatabasePDO::allowTransaction()

wire/core/FieldtypeMulti.php

@@ -209,7 +209,9 @@ abstract class FieldtypeMulti extends Fieldtype {
 
 		if(!$page->id || !$field->id) return false;
 	
+		/** @var WireDatabasePDO $database */
 		$database = $this->wire('database');
+		$useTransaction = $database->allowTransaction();
 		$values = $page->get($field->name);
 		$schema = array();
 		
@@ -228,10 +230,18 @@ abstract class FieldtypeMulti extends Fieldtype {
 		$table = $database->escapeTable($field->table); 
 		$page_id = (int) $page->id; 
 	
+		// use transaction when possible
+		if($useTransaction) $database->beginTransaction();
+
+		try {
 			// since we don't manage IDs of existing values for multi fields, we delete the existing data and insert all of it again
 			$query = $database->prepare("DELETE FROM `$table` WHERE pages_id=:page_id"); // QA
 			$query->bindValue(":page_id", $page_id, \PDO::PARAM_INT);
 			$query->execute();
+		} catch(\Exception $e) {
+			if($useTransaction) $database->rollBack();
+			throw $e;
+		}
 		
 		if(count($values)) {
 
@@ -284,21 +294,24 @@ abstract class FieldtypeMulti extends Fieldtype {
 				$sort++; 	
 			}	
 
-			$sql = rtrim($sql, ", "); 
-			$query = $database->prepare($sql);	
 			try {
+				$query = $database->prepare(rtrim($sql, ", "));	
 				$result = $query->execute();
 			} catch(\Exception $e) {
+				if($useTransaction) $database->rollBack();
 				if($this->wire('config')->allowExceptions) throw $e; // throw original
 				$msg = $e->getMessage();
 				if($this->wire('config')->debug && $this->wire('config')->advanced) $msg .= "\n$sql";
 				throw new WireException($msg); // throw WireException
 			}
 			
-			return $result; 
+		} else {
+			$result = true;
 		}
 
-		return true; 
+		if($useTransaction) $database->commit();
+
+		return $result; 
 	}
 	
 	/**

wire/core/WireDatabasePDO.php

@@ -332,7 +332,7 @@ class WireDatabasePDO extends Wire implements WireDatabase {
 	 * 
 	 */
 	public function inTransaction() {
-		return $this->pdo()->inTransaction();
+		return (bool) $this->pdo()->inTransaction();
 	}
 
 	/**
@@ -361,6 +361,22 @@ class WireDatabasePDO extends Wire implements WireDatabase {
 		return strtoupper($engine) === 'INNODB';
 	}
 
+	/**
+	 * Allow a new transaction to begin right now? (i.e. supported and not already in one)
+	 * 
+	 * Returns combined result of supportsTransaction() === true and inTransaction() === false.
+	 * 
+	 * #pw-group-PDO
+	 * 
+	 * @param string $table Optional table that transaction will be for
+	 * @return bool
+	 * @since 3.0.140
+	 * 
+	 */
+	public function allowTransaction($table = '') {
+		return $this->supportsTransaction($table) && !$this->inTransaction();
+	}
+
 	/**
 	 * Commits a transaction
 	 *