Re: Triggers on SELECT?

Tom Lane wrote:

> Josh Berkus <josh(at)agliodbs(dot)com> writes:
>> Now that we have Statement-level triggers, is there any reason we shouldn't
>> have triggers on SELECT?
>
> Plenty, although I'm too tired to recall 'em all. The fundamental
> problem with this is that it turns SELECT into an operation with
> side-effects.

The other fundamental problem is the definition of SELECT. To show just
one of the 273 possible problems:

UPDATE sometab SET foo = 'bar'
WHERE NOT EXISTS (SELECT 1 FROM othertab WHERE o_id = s_id);

Now explain in detail what the ON SELECT trigger on othertab will be
fired for.

Jan

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