Re: Confusing Trigger Docs.

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: neil(at)fairwindsoft(dot)com
Cc: pgsql-docs(at)postgresql(dot)org
Subject: Re: Confusing Trigger Docs.
Date: 2017-08-31 13:23:24
Message-ID: 20170831132324.GB2355@momjian.us
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Can someone help with this text? I think the author is right that it
needs correction or clarification.

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On Mon, Jul 3, 2017 at 08:07:10PM +0000, neil(at)fairwindsoft(dot)com wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/9.6/static/trigger-definition.html
> Description:
>
> https://www.postgresql.org/docs/devel/static/trigger-definition.html
>
> This sentence:
>
> &quot;If an INSERT contains an ON CONFLICT DO UPDATE clause, it is possible that
> the effects of all row-level BEFORE INSERT triggers and all row-level BEFORE
> UPDATE triggers can both be applied in a way that is apparent from the final
> state of the updated row, if an EXCLUDED column is referenced.&quot;
>
> is very hard to digest.
>
> Should &quot;is apparent&quot; really be &quot;is not apparent&quot;? If not, what does &quot;is
> apparent&quot; mean and why is this statement here?
>
> Then
>
> &quot;There need not be an EXCLUDED column reference for both sets of row-level
> BEFORE triggers to execute, though.&quot;
>
> Does this mean that both row level BEFORE INSERT and BEFORE UPDATE triggers
> are always executed when ON CONFLICT DO UPDATE clause is present? Or is
> there some circumstance where they are not?
>
> If so, does this also mean that if I have a single trigger defined as BEFORE
> UPDATE OR INSERT that this trigger will fire twice?
>
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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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