Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size

On 2022-06-23 Th 21:51, Andres Freund wrote:
> Hi,
>
> On 2022-06-23 16:38:12 +0900, Michael Paquier wrote:
>> On Tue, Jun 21, 2022 at 05:41:07PM -0400, Andrew Dunstan wrote:
>>> On 2022-06-21 Tu 17:25, Andres Freund wrote:
>>>> On 2022-06-21 17:11:33 -0400, Andrew Dunstan wrote:
>>>>> I and a couple of colleagues have looked it over. As far as it goes the
>>>>> json fix looks kosher to me. I'll play with it some more.
>>>> Cool.
>>>>
>>>> Any chance you could look at fixing the "structure" of the generated
>>>> expression "program". The recursive ExecEvalExpr() calls are really not ok...
>> By how much does the size of ExprEvalStep go down once you don't
>> inline the JSON structures as of 0004 in [1]?  And what of 0003?
> 0004 gets us back to 64 bytes, if 0003 is applied first. 0003 alone doesn't
> yield a size reduction, because obviously 0004 is the bigger problem. Applying
> just 0004 you end up with 88 bytes.
>
>
>> The JSON portions seem like the largest portion of the cake, though both are
>> must-fixes.
> Yep.
>
>
>>> Yes, but I don't guarantee to have a fix in time for Beta2.
>> IMHO, it would be nice to get something done for beta2.  Now the
>> thread is rather fresh and I guess that more performance study is
>> required even for 0004, so..
> I don't think there's a whole lot of performance study needed for 0004 - the
> current state is obviously wrong.
>
> I think Andrew's beta 2 comment was more about my other architectural
> complains around the json expression eval stuff.


Right. That's being worked on but it's not going to be a mechanical fix.


>
>
>> Waiting for beta3 would a better move at this stage.  Is somebody confident
>> enough in the patches proposed?
> 0001 is the one that needs to most careful analysis, I think. 0002 I'd be fine
> with pushing after reviewing it again. For 0003 David's approach might be
> better or worse, it doesn't matter much I think. 0004 is ok I think, perhaps
> with the exception of quibbling over some naming decisions?
>
>

The attached very small patch applies on top of your 0002 and deals with
the FmgrInfo complaint.


cheers


andrew


--
Andrew Dunstan
EDB: https://www.enterprisedb.com