It seems that solution with a shared lock on t1 is working. Though in this case I have the following questions:
1. If the session in which v1 was created is terminated abnormally, then there is a chance of the initial situation iteration, because v1 is a temporary view. What about this? 2. If I use an advisory lock instead of LOCK TABLE then what is the sequence of the following implicit objects deallocation: advisory locks and temporary views? As far as I understand from your reply, there is an unresolved problem of concurrent access to the system catalog in PostgreSQL, which was noticed in case which I have described. I understand that I should try not to execute DLL operators in concurrent transactions. However I cannot avoid it in my case. What can you suggest to do in this case, taking into account that PostgreSQL does not provide necessary stability? The main problem here is how to make safely the deletion of the temporary view (v1) in one session, and deletion of tables which are pointed by this temporary view (v1) in another session. Thank you. -----Original Message----- From: Tom Lane [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 28, 2007 10:02 PM To: Zubkovsky, Sergey Cc: pgsql-bugs@postgresql.org Subject: Re: [BUGS] ERROR: tuple concurrently updated "Zubkovsky, Sergey" <[EMAIL PROTECTED]> writes: > create table t1 ( id int ); > create temp view v1 as select * from t1; > C1: begin; drop view v1; > C2: drop table t1; > C1: commit; This seems a variant of the problem noted by Michael Fuhr some time ago: http://archives.postgresql.org/pgsql-hackers/2007-01/msg00937.php but I think it shows that the solution I proposed in that thread is still not adequate. To deal with the above, it seems like dropping v1 would have to acquire a shared lock on t1, thereby preventing the drop of t1 from starting until after v1 is safely gone. Or maybe have the drop of t1 recheck to see if v1 is still there after it has acquired lock on v1, but I'm afraid that might be too late to prevent an update conflict on the pg_depend row that both transactions want to delete. Ick. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
