From: | Michael Ansley <Michael(dot)Ansley(at)intec-telecom-systems(dot)com> |
---|---|
To: | "'Jan Wieck'" <janwieck(at)Yahoo(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org, pgsql-sql(at)postgreSQL(dot)org |
Subject: | RE: [SQL] Re: PL/pgsql EXECUTE 'SELECT INTO ...' |
Date: | 2001-02-08 13:35:14 |
Message-ID: | 7F124BC48D56D411812500D0B747251480F3E2@FILESERVER002 |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-sql |
What I wrote wasn't about temp tables, it was about selecting into plpgsql
variables. It would appear that Jan's syntax gets around this problem.
MikeA
-----Original Message-----
From: Jan Wieck [mailto:janwieck(at)Yahoo(dot)com]
Sent: 08 February 2001 13:30
To: Tom Lane
Cc: Jan Wieck; pgsql-hackers(at)postgreSQL(dot)org; pgsql-sql(at)postgreSQL(dot)org
Subject: [SQL] Re: PL/pgsql EXECUTE 'SELECT INTO ...'
Tom Lane wrote:
> I have looked a little bit at what it'd take to make SELECT INTO inside
> an EXECUTE work the same as it does in plain plpgsql --- that is, the
> INTO should reference plpgsql variables, not a destination table.
> It looks to me like this is possible but would require some nontrivial
> re-engineering inside plpgsql. What I'm visualizing is that EXECUTE
> should read its string argument not just as an SPI_exec() string, but
> as an arbitrary plpgsql proc_stmt. This would offer some interesting
> capabilities, like building a whole FOR-loop for dynamic execution.
> But there are a number of problems to be surmounted, notably arranging
> for the parsetree built by the plpgsql compiler not to be irretrievably
> memory-leaked. (That ties into something I'd wanted to do anyway,
> which is to have the plpgsql compiler build its trees in a memory
> context associated with the function, not via malloc().)
>
> This does not look like something to be tackling when we're already
> in late beta, unfortunately. So we have to decide what to do for 7.1.
> If we do nothing now, and then implement this feature in 7.2, we will
> have a backwards compatibility problem: EXECUTE 'SELECT INTO ...'
> will completely change in meaning.
>
> I am inclined to keep our options open by forbidding EXECUTE 'SELECT
> INTO ...' for now. That's more than a tad annoying, because that leaves
> no useful way to do a dynamically-built SELECT, but if we don't forbid
> it I think we'll regret it later.
You can do something like
FOR record_var IN EXECUTE <string-expr> LOOP
...
END LOOP;
In this case, the <string-expr> executed over SPI_exec() must
return tuples (0-n). Otherwise you'll get a runtime error.
Inside the loop you have access to the tuples via the record.
Is that the dynamically-built SELECT capability you've been
missing?
There's not that much need for mucking with temp tables in
EXECUTE as all this discussion looks to me.
Jan
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