-----Original Message-----
From: Peter T Mount <psqlhack@maidast.demon.co.uk>
To: Jan Wieck <jwieck@debis.com>
Cc: Bruce Momjian <maillist@candle.pha.pa.us>;
Andreas.Zeugswetter@telecom.at <Andreas.Zeugswetter@telecom.at>;
pgsql-hackers@hub.org <pgsql-hackers@hub.org>
Date: zondag 15 maart 1998 21:10
Subject: Re: [QUESTIONS] Re: [HACKERS] text should be a blob field
>On Wed, 4 Mar 1998, Jan Wieck wrote:
>
>> Bruce wrote:
>>
>> > > 1. Is there a call made by the backend to each datatype when a row is
>> > > deleted? I can't see one.
>> >
>> > Well, you could have a RULE that deletes the large object at row
>> > deletion time. However, if two rows point to the same large object,
the
>> > first one deleting it would delete the large object for the other. The
>> > only solution to this is to have a separate large object table, and use
>> > reference counts so only the last user of the object deletes it.
>>
>> I think triggers are more appropriate.
>>
>> On INSERT check that the large object referenced exists.
>>
>> On UPDATE if large object reference changes, check that new
>> large object exists and check if old large object isn't
>> referenced any more in which case drop the old large object.
>>
>> On DELETE check if large object isn't referenced any more ...
>>
>> Yes - I like triggers :-)
>
>I'm begining to agree with you here.
>
>So far, I've got the trigger to work, so if a row of a table is deleted,
>or an oid referencing a BLOB is updated, then the old BLOB is deleted.
>This removes the orphaned BLOB problem.
>
>The only problem I have now, is:
>
> How to get a trigger to be automatically created on a table when the
> table is created. This would be required, so the end user doesn't have
> to do this (normally from within an application).
>
>This would be required, esp. for expanding the text type (or memo, or
>whatever).
>
Since triggers are not inherited this doesn't seem appropiate too me -:(.
Won't user have to do some magic on inherited tables?
I think many things will be fixed when triggers, indices etc. are inherited
properly by derived classes.
With regards from,
Maurice.
