/**
* Gets information about changed records using a type and id and a logid.
* RedBean Locking shields you from race conditions by comparing the latest
* cached insert id with a the highest insert id associated with a write action
* on the same table. If there is any id between these two the record has
* been changed and RedBean will throw an exception. This function checks for changes.
* If changes have occurred it will throw an exception. If no changes have occurred
* it will insert a new change record and return the new change id.
* This method locks the log table exclusively.
*
* @param string $type type
* @param integer $id id
* @param integer $logid log id
*
* @return integer $newchangeid new id
*/
public function checkChanges($type, $id, $logid) {
$type = $this->writer->check($type);
$id = (int) $id;
$logid = (int) $logid;
$num = $this->adapter->getCell("
SELECT count(*) FROM __log WHERE tbl=\"$type\" AND itemid=$id AND action=2 AND id > $logid");
if ($num) {
throw new RedBean_Exception_FailedAccessBean("Locked, failed to access (type:$type, id:$id)");
}
$this->adapter->exec("INSERT INTO __log (id,action,tbl,itemid) VALUES(NULL, 2,:tbl,:id)",array(":tbl"=>$type, ":id"=>$id));
$newid = $this->adapter->getInsertID();
if ($this->adapter->getCell("select id from __log where tbl=:tbl AND id < $newid and id > $logid and action=2 and itemid=$id ",
array(":tbl"=>$type))) {
throw new RedBean_Exception_FailedAccessBean("Locked, failed to access II (type:$type, id:$id)");
}
return $newid;
}