Deadlock with single update statement?

Rob Nikander <rob.nikander@xxxxxxxxx> · Sat, 10 Jun 2017 06:26:26 -0400

Hi,

I’m trying to track down a deadlock happening in a live app. I’m wondering about statements like this, which select more than one row to update:

     update t set num = 1 where name = ‘foo’;

It appears to be causing a deadlock, but I can’t reproduce it on my test database. Could two threads, each running this update, get in a deadlock? In other words, are both of the following true:

1. The update locks each row in sequence, not all at once.
2. The order of the row locking could vary from one thread to the next.

thanks,
Rob

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