Date: Wed, 6 Nov 2019 12:11:12 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>,
	Mark Dilger <hornschnorter@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Checking return value of SPI_execute
Message-ID: <20191106151112.GA12251@alvherre.pgsql>
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On 2019-Nov-06, Pavel Stehule wrote:

> My comment was about maybe obsolescence of this API. Probably it was
> designed before exception introduction.
> 
> For example - syntax error is ended by exception. Wrong numbers of argument
> is signalized by error status. I didn't study this code, but maybe was much
> more effective to raise exceptions inside SPI instead return status code.
> These errors are finished by exceptions, but these exceptions coming from
> different places. For me it looks strange, if some functions returns error
> status, but can be ended by exception too.

Yeah, I think I'd rather have more status codes and less exceptions,
than the other way around.  The problem with throwing exceptions for
every kind of error is that we don't allow exceptions to be caught (per
project policy) except to be rethrown.  It seems like for errors where
the SPI code can clean up its own resources (free memory, close portals
etc), it should do such cleanup then return SPI_SYNTAX_ERROR or whatever
and the caller can decide whether to turn this into an exception or
handle in a different way; whereas for exceptions thrown by callees (say
OOM) it would just propagate the exception.  This mean callers are
forced into adding code to check for return codes, but it allows more
flexibility.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services