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Re: Progress of asynchronous queries

From: Adriaan van Os <adriaan(at)microbizz(dot)nl>
To: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: Progress of asynchronous queries
Date: 2006-09-18 07:51:34
Message-ID: 450E5006.8020603@microbizz.nl (view raw or flat)
Thread:
Lists: pgsql-interfaces
Jeroen T. Vermeulen wrote:
> On Sun, September 17, 2006 17:22, Adriaan van Os wrote:
> 
>>> But you'd be doing this in a transaction anyway: you can't declare a
>>> cursor without starting a transaction first.Yes, you could deliberately
>>> declare "WITH HOLD" and keep using your cursor after commiting or
>>> aborting
>>> the transaction.  But even then, so far as I know, the cursor presents a
>>> snapshot view of its result set so you get an effective isolation level
>>> of
>>> "serializable" even then.
>> No, carefully read
>> <http://www.postgresql.org/docs/8.1/static/transaction-iso.html>.
> 
> I'm familiar with the document, thank you, but if you're not prepared to
> give any detail beyond "no" then I remain unconvinced.  What part exactly
> do you disagree with?  That cursors can't be declared without beginning a
> transaction first?  That cursors present a snapshot view of their result
> set?  That that amounts to an effective isolation level of "serializable?"

I now read that Postgres only supports FOR READ ONLY cursors. So, yes, for those cursors you are 
right and my remark doesn't apply.

Still, the issue I raised was about tracing the progress of a SQL command in general, not about the 
specific case of using a cursor instead.

Regards,

Adriaan van Os

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