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Re: Avoid orphaned objects dependencies, take 3

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Alexander Lakhin <exclusion@gmail.com>, pgsql-hackers@lists.postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2024-10-28T09:30:19Z
Lists: pgsql-hackers

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Hi,

On Mon, Aug 19, 2024 at 03:35:14PM +0000, Bertrand Drouvot wrote:
> Hi,
> 
> On Wed, Jul 10, 2024 at 07:31:06AM +0000, Bertrand Drouvot wrote:
> > So, to sum up:
> > 
> > A. Locking is now done exclusively with LockNotPinnedObject(Oid classid, Oid objid)
> > so that it's now always clear what object we want to acquire a lock for. It means
> > we are not manipulating directly an object address or a list of objects address
> > as it was the case when the locking was done "directly" within the dependency code.
> > 
> > B. A special case is done for objects that belong to the RelationRelationId class.
> > For those, we should be in one of the two following cases that would already
> > prevent the relation to be dropped:
> > 
> >  1. The relation is already locked (could be an existing relation or a relation
> >  that we are creating).
> > 
> >  2. The relation is protected indirectly (i.e an index protected by a lock on
> >  its table, a table protected by a lock on a function that depends the table...)
> > 
> > To avoid any risks for the RelationRelationId class case, we acquire a lock if
> > there is none. That may add unnecessary lock for 2. but that seems worth it. 
> > 
> 
> Please find attached v16, mandatory rebase due to 80ffcb8427.

rebased (v17 attached).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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  1. Avoid orphaned objects dependencies

  2. Don't try to record dependency on a dropped column's datatype