Thread

1. AW: The lightbulb just went on...

   Zeugswetter Andreas SB <zeugswettera@wien.spardat.at> — 2000-10-19T08:21:04Z

   > what happens to sessions is that it does:
   > 
   > SELECT session_data, id 
   > FROM   sessions
   > WHERE  id = ?
   > FOR UPDATE
   > 
   > .... client does some processing ...
   > 
   > UPDATE sesssions set session_data = ? WHERE id = ?;
   > 
   > (this is where the error happens)
   > 
   > I think part of my problem might be that sessions is a view 
   > and not a table,
   
   Did you create an on update do instead rule ?
   
   This is currently not done automatically for views,
   thus views without additional "create rule"s are select only.
   
   But, I am wondering whether the "for update" places the correct lock ?
   
   Andreas
   
   

2. Re: AW: The lightbulb just went on...

   Tom Lane <tgl@sss.pgh.pa.us> — 2000-10-19T14:11:58Z

   Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:
   >> SELECT session_data, id 
   >> FROM   sessions
   >> WHERE  id = ?
   >> FOR UPDATE
   >>
   >> I think part of my problem might be that sessions is a view 
   >> and not a table,
   
   > Did you create an on update do instead rule ?
   > This is currently not done automatically for views,
   > thus views without additional "create rule"s are select only.
   > But, I am wondering whether the "for update" places the correct lock ?
   
   Hmm, good point!  I'm not sure what "select for update" on a view ought
   to do, but I am pretty sure that the code will not do anything useful
   or sensible for this case...
   
   			regards, tom lane
   
   

3. Re: AW: The lightbulb just went on...

   Michael J Schout <mschout@gkg.net> — 2000-10-23T04:46:35Z

   
   On Thu, 19 Oct 2000, Tom Lane wrote:
   
   > Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:
   > >> SELECT session_data, id 
   > >> FROM   sessions
   > >> WHERE  id = ?
   > >> FOR UPDATE
   > >>
   > >> I think part of my problem might be that sessions is a view 
   > >> and not a table,
   > 
   > > Did you create an on update do instead rule ?
   
   Yes actually :).
   
   But Ive since elimintated the rule and figured out I could get
   the equivalent functionality I was getting the the RULE/VIEW by just 
   using a simple PL/pgSQL trigger.
   
   Since doing that, the "relation XXXXX modified while in use" errors
   have gone away, but I'm still not sure I trust VACUUM ANALYZE enough
   to run it on a non-idle production database :).  I want to do more
   testing before I get that brave :).
   
   Mike