


>From: Tom Lane <tgl@sss.pgh.pa.us>
>To: "Jenny -" <nat_lazy@hotmail.com>
>Subject: Re: [HACKERS] this is in plain text (row level locks) Date: Sat, 
>02 Aug 2003 23:28:30 -0400
>
> > if row-level locks are not recorded in proclock or any other shared 
>memory
> > datastructuers, then why does lockmode (array or ints) of proclock 
>indicate
> > that an AccessShareLock is acquired when a row is locked by 
>application.?
>
>That's a table lock --- it's independent of row locks.  It's there
>mostly to ensure someone doesn't delete the whole table out from under
>you.
>
>			regards, tom lane

so even though the application locks a row in a table, table-level locks are 
automatically taken by postgesql ? why is that?
thanks

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Tue, 05 Aug 2003 10:57:23 -0700
"Jenny -" <nat_lazy@hotmail.com>
Re: this is in plain text (row level locks)
"Jenny -" <nat_lazy@hotmail.com> writes:
> so even though the application locks a row in a table, table-level locks are 
> automatically taken by postgesql ? why is that?

So that the table doesn't disappear while you're trying to scan it.  (Or
afterwards --- a row-level lock wouldn't be noticed by DROP TABLE.)

Note that AccessShareLock is a pretty weak kind of lock, and holding it
does not prevent most other operations.

			regards, tom lane

Tue, 05 Aug 2003 15:02:10 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: this is in plain text (row level locks) 