PG_RE_THROW is mandatory (was Re: jsonpath)
PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Alvaro Herrera <alvherre@2ndquadrant.com>
Дата:
In https://postgr.es/m/1676.1548726280@sss.pgh.pa.us Tom Lane wrote:
> Sure: every errcode we have is unsafe to treat this way.
>
> The backend coding rule from day one has been that a thrown error requires
> (sub)transaction cleanup to be done to make sure that things are back in a
> good state. You can *not* just decide that it's okay to ignore that,
> especially not when invoking code outside the immediate area of what
> you're doing.
elog.h claims that PG_RE_THROW is "optional":
/*----------
* API for catching ereport(ERROR) exits. Use these macros like so:
*
* PG_TRY();
* {
* ... code that might throw ereport(ERROR) ...
* }
* PG_CATCH();
* {
* ... error recovery code ...
* }
* PG_END_TRY();
*
* (The braces are not actually necessary, but are recommended so that
* pgindent will indent the construct nicely.) The error recovery code
* can optionally do PG_RE_THROW() to propagate the same error outwards.
This is obviously wrong; while we have a couple of codesites that omit
it, it's not a generally available coding pattern. I think we should
amend that comment. I propose: "The error recovery code must normally
do PG_RE_THROW() to propagate the error outwards; failure to do so may
leave the system in an inconsistent state for further processing."
Other wording proposals welcome, but I don't want to leave it as is.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Re: PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Andres Freund <andres@anarazel.de>
Дата:
On 2019-02-06 13:09:59 -0300, Alvaro Herrera wrote:
> In https://postgr.es/m/1676.1548726280@sss.pgh.pa.us Tom Lane wrote:
>
> > Sure: every errcode we have is unsafe to treat this way.
> >
> > The backend coding rule from day one has been that a thrown error requires
> > (sub)transaction cleanup to be done to make sure that things are back in a
> > good state. You can *not* just decide that it's okay to ignore that,
> > especially not when invoking code outside the immediate area of what
> > you're doing.
>
> elog.h claims that PG_RE_THROW is "optional":
>
> /*----------
> * API for catching ereport(ERROR) exits. Use these macros like so:
> *
> * PG_TRY();
> * {
> * ... code that might throw ereport(ERROR) ...
> * }
> * PG_CATCH();
> * {
> * ... error recovery code ...
> * }
> * PG_END_TRY();
> *
> * (The braces are not actually necessary, but are recommended so that
> * pgindent will indent the construct nicely.) The error recovery code
> * can optionally do PG_RE_THROW() to propagate the same error outwards.
>
> This is obviously wrong; while we have a couple of codesites that omit
> it, it's not a generally available coding pattern. I think we should
> amend that comment. I propose: "The error recovery code must normally
> do PG_RE_THROW() to propagate the error outwards; failure to do so may
> leave the system in an inconsistent state for further processing."
Well, but it's ok not to rethrow if you do a [sub]transaction
rollback. I assume that's why it's framed as optional. We probably
should reference that fact?
Greetings,
Andres Freund
Re: PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Alvaro Herrera <alvherre@2ndquadrant.com>
Дата:
> On 2019-02-06 13:09:59 -0300, Alvaro Herrera wrote: > > This is obviously wrong; while we have a couple of codesites that omit > > it, it's not a generally available coding pattern. I think we should > > amend that comment. I propose: "The error recovery code must normally > > do PG_RE_THROW() to propagate the error outwards; failure to do so may > > leave the system in an inconsistent state for further processing." On 2019-Feb-06, Andres Freund wrote: > Well, but it's ok not to rethrow if you do a [sub]transaction > rollback. I assume that's why it's framed as optional. We probably > should reference that fact? On 2019-Feb-06, Tom Lane wrote: > Well, it can either do PG_RE_THROW or do a (sub)transaction abort. > Some level of throw-catching code has to do the latter eventually. So, "The error recovery code can either do PG_RE_THROW to propagate the error outwards, or do a (sub)transaction abort. Failure to do so may leave the system in an inconsistent state for further processing." -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Re: PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Alvaro Herrera <alvherre@2ndquadrant.com>
Дата:
On 2019-Feb-07, Tom Lane wrote: > Alvaro Herrera writes: > > So, > > > "The error recovery code can either do PG_RE_THROW to propagate the > > error outwards, or do a (sub)transaction abort. Failure to do so may > > leave the system in an inconsistent state for further processing." > > WFM. Thanks, pushed. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Re: PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Alvaro Herrera writes: > So, > "The error recovery code can either do PG_RE_THROW to propagate the > error outwards, or do a (sub)transaction abort. Failure to do so may > leave the system in an inconsistent state for further processing." WFM. regards, tom lane
Re: PG_RE_THROW is mandatory (was Re: jsonpath)
От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Alvaro Herrera writes: > elog.h claims that PG_RE_THROW is "optional": > * (The braces are not actually necessary, but are recommended so that > * pgindent will indent the construct nicely.) The error recovery code > * can optionally do PG_RE_THROW() to propagate the same error outwards. > This is obviously wrong; while we have a couple of codesites that omit > it, it's not a generally available coding pattern. I think we should > amend that comment. I propose: "The error recovery code must normally > do PG_RE_THROW() to propagate the error outwards; failure to do so may > leave the system in an inconsistent state for further processing." Well, it can either do PG_RE_THROW or do a (sub)transaction abort. Some level of throw-catching code has to do the latter eventually. regards, tom lane
