Re: Strange behavior of function date_trunc

On 05.05.2021 17:11, Tom Lane wrote:
> Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> writes:
>> On 5/5/21 3:23 PM, Pavel Luzanov wrote:
>>> It is very likely that the date_trunc function in the following
>>> example is executed for each line of the query. Although it marked
>>> as a STABLE and could only be called once.
>> It could, but that's just an option - the database may do that, but
>> it's not required to do it. In this case it might be beneficial, but
>> it'd make the planner more complex etc.
> Yeah, there simply is not any provision for caching the results of
> stable functions in the way Pavel seems to be imagining. People have
> played around with patches for that, but nothing's been accepted.

Thank you for the clarification. It's not very obvious, at least for me.

--
Pavel Luzanov
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