![]() Per second averages calculated from the last 2 seconds Mysql> insert into tc values('az', 0, 'aa') on duplicate key update c1=c1+1 Query OK, 0 rows affected, 1 warning (0.02 sec) Mysql> create table innodb_lock_monitor(id int) engine=InnoDB Mysql> create table tc(id char(2) primary key, c1 int, c2 char(2)) ON DUPLICATE KEY UPDATE statement, while in reality it does NOT happen: One may expect to see this next-key lock for ANY kind on INSERT. ON DUPLICATE KEY UPDATE differs from a simple INSERT in that an exclusive next-key lock rather than a shared lock is placed on the row to be updated when a duplicate-key error occurs." ON DUPLICATE KEY UPDATE manual just says: Note that in the above (or anywhere on that page) there is no clarification on what kind of key this "duplicate-key error" applies, PRIMARY or some secondary UNIQUE key (there can be many). This use of a shared lock can result in deadlock should there be multiple sessions trying to insert the same row if another session already has an exclusive lock." "If a duplicate-key error occurs, a shared lock on the duplicate index record is set. This lock is an index-record lock, not a next-key lock (that is, there is no gap lock) and does not prevent other sessions from inserting into the gap before the inserted row." If you have the time to read on you will, in a very short time, learn to save major frustration, wasted time and money."INSERT sets an exclusive lock on the inserted row. ![]() We have prepared this guide so that you can put our knowledge into action and organize your keys effectively and efficiently. Sure Lock & Key is a locksmith company, coast to coast, with over 35 years of experience in the industry. ![]() In fact, we would estimate that at least 7 out of 10 calls we receive for our key cutting service could have been avoided if our client had created a strategy for storing their keys. It’s one of the services we perform often, believe it or not. Helping people in this scenario is something we do all the time. Just the weight or the possibility of losing or misplacing one or all of the keys. Now imagine the stress they must be under. However, imagine how many keys, business owners, people who work in big companies, etc, have to carry. It safely lays somewhere in the depth of our bag, waiting to cause inconvenience when we need to unlock a door quickly. ![]() If you’ve ever had to carry such a thing, you know what we mean. The truth is nobody really wants to be burdened with such a bulky item. Most people can carry, let's say, around ten keys, and that's a huge number. It may be an excellent try to at least decrease the unwanted duplication, but it’s clearly not something you can rely on. The sense of security they may give you is not supported by any means. It also means that these keys don’t increase security since there’s no special mechanism to make the duplication impossible except for the warning on the label, which obviously might not be enough. The “do not duplicate” label means that the original owner wants, or has wanted, to cease the unauthorized key duplication. Key duplication is still more accessible than it may seem. If you purchased a premise and got a set of keys with “do not duplicate” stamped on each of them, don’t worry. Can I duplicate this key? Is it pointless to ask a locksmith to make a copy of this key? Or maybe it’s even illegal to ask a locksmith to duplicate this key? Sometimes, people may consider getting a new lock because they think it would be easier than bothering with a key that forbids duplication. Keys with the “do not duplicate” label raise many questions.
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