Horton

Re: SIREAD lock versus ACCESS EXCLUSIVE lock

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>, pgsql-hackers@postgresql.org, "<Simon Riggs" <simon@2ndquadrant.com>, Dan Ports <drkp@csail.mit.edu>
Date: 2011-06-04T16:20:52Z
Lists: pgsql-hackers 
On 04.06.2011 19:19, Tom Lane wrote:
> Heikki Linnakangas<heikki.linnakangas@enterprisedb.com>  writes:
>> On 03.06.2011 21:04, Kevin Grittner wrote:
>>> Also, if anyone has comments or hints about the placement of those
>>> calls, I'd be happy to receive them.
>
>> heap_drop_with_catalog() schedules the relation for deletion at the end
>> of transaction, but it's still possible that the transaction aborts and
>> the heap doesn't get dropped after all. If you put the
>> DropAllPredicateLocksFromTable() call there, and the transaction later
>> aborts, you've lost all the locks already.
>
> But on the third thought: is that wrong?  Surely locks taken by an
> aborted transaction can be discarded.

These are predicate locks - there can be "locks" on the table belonging 
to transactions that have already committed.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com