perl - DBD::SQLite: Insert or Update - Question -

while writing question (howto: insert new entry , if exists already, update it) found answers in related questions:

$sql = "insert or replace $table ( id, name, rating ) values( ?, ?, ? )"; $sth_rating = $dbh->prepare( $sql ); $sth_rating->execute( $id, $name, $rating ); 

.

$sql = "insert or ignore $table ( id, name, rating ) values ( ?, ?, ? )"; $sth_rating = $dbh->prepare( $sql ); $sth_rating->execute( $id, $name, $rating );  $sql = "update $table set rating = ? id = ?"; $sth_rating = $dbh->prepare( $sql ); $sth_rating->execute( $rating, $id ); 

is second method more safe first one?

the second method less safe because non-atomic. in other words, happens in more 1 step. consider 2 processes both updating same data. time moving down.

process 1                      process 2  insert or ignore...                                insert or ignore...                                update... update... 

process 1 starts first, process 2 sneaks in , update between. process 1 blows right on process 2's update.

this isn't bad in particular situation, both processes going blow on each other no matter what, can trouble extending technique.

(unless misunderstood question , want upsert)