Re: pre-commit triggers

On Tue, Nov 19, 2013 at 12:45 AM, Noah Misch <noah(at)leadboat(dot)com> wrote:
> On Fri, Nov 15, 2013 at 01:01:48PM -0500, Andrew Dunstan wrote:
>> The triggers don't fire if there is no real XID, so only actual data
>> changes should cause the trigger to fire.
>
> What's the advantage of this provision? Without it, an individual trigger
> could make the same check and drop out quickly. A trigger not wanting it
> can't so easily work around its presence, though. Heretofore, skipping XID
> assignment has been an implementation detail that improves performance without
> otherwise calling user attention to itself. This provision would make the
> decision to acquire an XID (where optional) affect application behavior.

Yeah, I agree that that's an ugly wart. If we want a pre-commit
trigger that's only called for transactions that write data, we at
least need to name it appropriately.

--
Robert Haas
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