Clarify how triggers relate to transactions

On Tue, 2021-04-27 at 14:26 +0000, PG Doc comments form wrote:

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/13/sql-createtrigger.html
Description:

https://www.postgresql.org/docs/current/sql-createtrigger.html mentions the
word "transaction" only once, in reference specifically to constraint
triggers: "They can be fired either at the end of the statement causing the
triggering event, or at the end of the containing transaction; in the latter
case they are said to be deferred."

If I understand correctly, it would be helpful to add this sentence or a
corrected version of it: "Triggers always execute in the same transaction as
the triggering event, and if a trigger fails, the transaction is rolled
back."

Good idea in principle, but I'd put that information on
https://www.postgresql.org/docs/current/trigger-definition.html

Yours,
Laurenz Albe

Gotcha. Where would I go to make the PR?

On Wed, Apr 28, 2021, 7:24 AM Laurenz Albe <laurenz.albe@cybertec.at> wrote:

On Wed, 2021-04-28 at 13:18 -0400, Nathan Long wrote:

Gotcha. Where would I go to make the PR?

You'd create a patch against Git master and send it to this
mailing list or pgsql-hackers. If you don't want it to fall
between the cracks, register in the next commitfest where it
can undergo peer review.

Yours,
Laurenz Albe

On Wed, Apr 28, 2021, at 2:18 PM, Nathan Long wrote:

Gotcha. Where would I go to make the PR?

There is no such PR feature; we don't use GitHub despite of having a mirror
there. As Laurenz said you should create a patch (using your preferred git
command) and attach to this thread. If you prefer, you can also send the patch
to pgsql-hackers ML (add the link to this thread). The next step is to register
your patch to the next commitfest [1]https://commitfest.postgresql.org/33/ so we don't lose track of it. For a
complete reference about submitting a patch, take a look at [2]https://wiki.postgresql.org/wiki/Submitting_a_Patch.

[1]: https://commitfest.postgresql.org/33/
[2]: https://wiki.postgresql.org/wiki/Submitting_a_Patch

Regards,

--
Euler Taveira
EDB https://www.enterprisedb.com/

On Wed, 2021-04-28 at 13:24 +0200, Laurenz Albe wrote:

On Tue, 2021-04-27 at 14:26 +0000, PG Doc comments form wrote:

https://www.postgresql.org/docs/current/sql-createtrigger.html mentions the
word "transaction" only once, in reference specifically to constraint
triggers: "They can be fired either at the end of the statement causing the
triggering event, or at the end of the containing transaction; in the latter
case they are said to be deferred."

If I understand correctly, it would be helpful to add this sentence or a
corrected version of it: "Triggers always execute in the same transaction as
the triggering event, and if a trigger fails, the transaction is rolled
back."

Good idea in principle, but I'd put that information on
https://www.postgresql.org/docs/current/trigger-definition.html

Here is a proposed patch for this.

Yours,
Laurenz Albe

On Wed, 2021-05-05 at 11:55 +0200, Laurenz Albe wrote:

On Wed, 2021-04-28 at 13:24 +0200, Laurenz Albe wrote:

On Tue, 2021-04-27 at 14:26 +0000, PG Doc comments form wrote:

https://www.postgresql.org/docs/current/sql-createtrigger.html mentions the
word "transaction" only once, in reference specifically to constraint
triggers: "They can be fired either at the end of the statement causing the
triggering event, or at the end of the containing transaction; in the latter
case they are said to be deferred."

If I understand correctly, it would be helpful to add this sentence or a
corrected version of it: "Triggers always execute in the same transaction as
the triggering event, and if a trigger fails, the transaction is rolled
back."

Good idea in principle, but I'd put that information on
https://www.postgresql.org/docs/current/trigger-definition.html

Here is a proposed patch for this.

Replying to -hackers for the commitfest app.

Yours,
Laurenz Albe

Laurenz Albe <laurenz.albe@cybertec.at> writes:

On Wed, 2021-04-28 at 13:24 +0200, Laurenz Albe wrote:

On Tue, 2021-04-27 at 14:26 +0000, PG Doc comments form wrote:

If I understand correctly, it would be helpful to add this sentence or a
corrected version of it: "Triggers always execute in the same transaction as
the triggering event, and if a trigger fails, the transaction is rolled
back."

Good idea in principle, but I'd put that information on
https://www.postgresql.org/docs/current/trigger-definition.html

Here is a proposed patch for this.

I think this is a good idea, but I felt like you'd added the extra
sentences in not-terribly-well-chosen places. For instance, your
first addition in trigger.sgml is adding to a para that talks about
triggers for tables, while the next para talks about triggers for
views. So it seems unclear whether the statement is meant to apply
to view triggers too.

I think it'd work out best to make this a separate para after the
one that defines before/after/instead-of triggers. How do you
like the attached?

regards, tom lane

On Fri, 2021-07-30 at 16:20 -0400, Tom Lane wrote:

Laurenz Albe <laurenz.albe@cybertec.at> writes:

On Wed, 2021-04-28 at 13:24 +0200, Laurenz Albe wrote:

On Tue, 2021-04-27 at 14:26 +0000, PG Doc comments form wrote:

If I understand correctly, it would be helpful to add this sentence or a
corrected version of it: "Triggers always execute in the same transaction as
the triggering event, and if a trigger fails, the transaction is rolled
back."

Here is a proposed patch for this.

I think this is a good idea, but I felt like you'd added the extra
sentences in not-terribly-well-chosen places. For instance, your
first addition in trigger.sgml is adding to a para that talks about
triggers for tables, while the next para talks about triggers for
views. So it seems unclear whether the statement is meant to apply
to view triggers too.

I think it'd work out best to make this a separate para after the
one that defines before/after/instead-of triggers. How do you
like the attached?

That is better, and I like your patch. Thanks!
Keeping paragraphs short is a good thing.

Yours,
Laurenz Albe

Laurenz Albe <laurenz.albe@cybertec.at> writes:

On Fri, 2021-07-30 at 16:20 -0400, Tom Lane wrote:

I think it'd work out best to make this a separate para after the
one that defines before/after/instead-of triggers. How do you
like the attached?

That is better, and I like your patch. Thanks!
Keeping paragraphs short is a good thing.

Pushed like that, then.

regards, tom lane