Re: Locks on temp table and PREPARE

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От Emmanuel Cecchet
Тема Re: Locks on temp table and PREPARE
Дата
Msg-id 4A26E226.1000706@frogthinker.org
обсуждение исходный текст
Ответ на Re: Locks on temp table and PREPARE  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Locks on temp table and PREPARE  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Locks on temp table and PREPARE  (Alvaro Herrera <alvherre@commandprompt.com>)
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Tom Lane wrote:
> True, but the problem is that the tuple might still be live to (some
> snapshots in) that transaction, so we can't inject a duplicate tuple
> without risking confusing it.  In this particular case that isn't an
> issue because the transaction is done executing, but the tqual.c
> rules don't know that.
>   
Please excuse my ignorance. I am not sure to get how the tuple could 
still be live to some snapshots after the transaction has prepared. What 
could still happen to objects that were only visible to a transaction 
after it has prepared? An example would definitely help.
Is it possible in Postgres for a transaction to see an object that was 
created inside another transaction before it commits (assuming at least 
'read committed' of course)?

Thanks again,
Emmanuel


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