From: Adrian Klaver <adrian.klaver@aklaver.com>
To: Michael Moore <michaeljmoore@gmail.com>
To: David G. Johnston <david.g.johnston@gmail.com>
Cc: postgres list <pgsql-sql@postgresql.org>
Subject: Re: Why does the PL/pgSQL compiler do this?
Date: Mon, 31 Oct 2016 16:38:54 -0700
Message-ID: <0520e6e1-8708-f58a-af0b-5624df7d01cf@aklaver.com> (raw)
In-Reply-To: <CACpWLjMz+wvWLFQnaiA6pamqG2YJuahSWRhf-ov+Dfd7uXf8pw@mail.gmail.com>
References: <CACpWLjOkzeKNNLccAnR7EyMYH+4w8SnhEve43rD+VLoXQ4ROEw@mail.gmail.com>
<CAKFQuwYjBuTC59cnndRBb=42g0Y4DLQDx1Tm0JSROGTq0R0mFA@mail.gmail.com>
<CACpWLjOVudD-7JEVu=u4UUMWLQeAoQzfAiPwj9xjPnBqWHxKnw@mail.gmail.com>
<CACpWLjMz+wvWLFQnaiA6pamqG2YJuahSWRhf-ov+Dfd7uXf8pw@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-sql>
On 10/31/2016 04:32 PM, Michael Moore wrote:
> I'm still a bit confused. If I replace the ROLLBACK; command with
> ELEPHANT; the result is a syntax error. Why doesn't ROLLBACK; produce
> the same error since it is not valid in the LANGUAGE plpgsql. I
> understand that "ROLLBACK TO SAVEPOINT" IS valid. But it's not the same
> thing.
I am guessing this:
https://www.postgresql.org/docs/9.5/static/plpgsql-implementation.html
" A disadvantage is that errors in a specific expression or command
cannot be detected until that part of the function is reached in
execution. (Trivial syntax errors will be detected during the initial
parsing pass, but anything deeper will not be detected until execution.)"
ROLLBACK might actually be valid at some point, ELEPHANT will not so it
caught in the trivial error stage.
>
> On Mon, Oct 31, 2016 at 3:55 PM, Michael Moore <michaeljmoore@gmail.com
> <mailto:michaeljmoore@gmail.com>> wrote:
>
> Cool, thanks David, I'll give it a read.
>
>
> On Mon, Oct 31, 2016 at 3:24 PM, David G. Johnston
> <david.g.johnston@gmail.com <mailto:david.g.johnston@gmail.com>> wrote:
>
> On Mon, Oct 31, 2016 at 3:13 PM, Michael Moore
> <michaeljmoore@gmail.com <mailto:michaeljmoore@gmail.com>>wrote:
>
> Here is the complete function, but all you need to look at
> is the exception block. (I didn't write this code) :-) I
> will ask the question after the code.
> [...]
>
> RETURN TRUE;
>
> EXCEPTION WHEN OTHERS THEN
>
> RAISE EXCEPTION '% %', SQLERRM, SQLSTATE;
>
> ROLLBACK;
>
> RETURN FALSE;
>
> END;
>
> $BODY$
>
> LANGUAGE plpgsql VOLATILE
>
> COST 100;
>
>
> So, here is the question. Why does the compiler not catch:
>
> 1) ROLLBACK; is not a valid PL/pgSQL command
>
>
> R
> eading section 41.10.2 at the linked page should answer this part.
>
> https://www.postgresql.org/docs/current/static/plpgsql-implementation.html
> <https://www.postgresql.org/docs/current/static/plpgsql-implementation.html;
>
>
> 2) ROLLBACK; and RETURN FALSE; can never be reached
>
>
>
> Similar to the above - though "static analysis" is yet a step
> beyond even what the syntax checking skipping covered above
> would reveal.
>
> David J.
>
>
>
--
Adrian Klaver
adrian.klaver@aklaver.com
--
Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: adrian.klaver@aklaver.com, michaeljmoore@gmail.com, david.g.johnston@gmail.com
Subject: Re: Why does the PL/pgSQL compiler do this?
In-Reply-To: <0520e6e1-8708-f58a-af0b-5624df7d01cf@aklaver.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox