Re: Doubt about AccessExclusiveLock in ALTER TABLE .. SET ( .. );

<div dir="ltr"><div class="gmail_extra"><br />On Tue, Apr 7, 2015 at 10:15 PM, Alvaro Herrera <<a
href="mailto:alvherre@2ndquadrant.com">alvherre@2ndquadrant.com</a>>wrote:<br />><br />> Fabrízio de Royes
Mellowrote:<br />> > On Mon, Apr 6, 2015 at 12:53 AM, Alvaro Herrera <<a
href="mailto:alvherre@2ndquadrant.com">alvherre@2ndquadrant.com</a>><br/>> > wrote:<br />> > ><br
/>>> > Fabrízio de Royes Mello wrote:<br />> > ><br />> > > > Ok guys. The attached patch
refactorthe reloptions adding a new field<br />> > > > "lockmode" in "relopt_gen" struct and a new method
todetermine the<br />> > > > required lock level from an option list.<br />> > > ><br />>
>> > We need determine the appropriate lock level for each reloption:<br />> > ><br />> > >
Idon't think AccessShareLock is appropriate for any option change.  You<br />> > > should be using a lock
levelthat's self-conflicting, as a minimum<br />> > > requirement, to avoid two processes changing the value
concurrently.<br/>> ><br />> > What locklevel do you suggest? Maybe ShareLock?<br />><br />>
ShareUpdateExclusiveprobably.  ShareLock doesn't conflict with itself.<br />><br /><br /></div><div
class="gmail_extra">Ok.<br/><br /></div><div class="gmail_extra"><br />> > > (I would probably go as far as
ensuringthat the lock level specified in<br />> > > the table DoLockModesConflict() with itself in an Assert
somewhere.)<br/>> ><br />> > If I understood this is to check if the locklevel of the reloption list<br
/>>> don't conflict one each other, is it?<br />><br />> I mean<br />>        
Assert(DoLockModesConflict(relopt_gen->locklevel,relopt_gen->locklevel));<br />><br /><br /></div><div
class="gmail_extra">Understood...IMHO the better place to perform this assert is in "initialize_reloptions".<br
/></div><divclass="gmail_extra"><br /></div><div class="gmail_extra">Thoughts?<br /><br /></div><div
class="gmail_extra">--<br/>Fabrízio de Royes Mello<br />Consultoria/Coaching PostgreSQL<br />>> Timbira: <a
href="http://www.timbira.com.br">http://www.timbira.com.br</a><br/>>> Blog: <a
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