Re: eval_const_expresisions and ScalarArrayOpExpr

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: eval_const_expresisions and ScalarArrayOpExpr
Date: 2017-05-11 16:20:55
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On 05/11/2017 06:21 PM, Tom Lane wrote:
> Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
>> Eval_const_expressions() doesn't know about ScalarArrayOpExpr.
>> ...
>> That seems like an oversight. I guess that scenario doesn't happen very
>> often in practice, but there's no reason not to do it when it does.
>> Patch attached.
> Yeah, I think it's a lack-of-round-tuits situation. Your patch reminds
> me of a more ambitious attempt I made awhile back to reduce the amount
> of duplicative boilerplate in eval_const_expressions. I think I wrote
> it during last year's beta period, stashed it because I didn't feel like
> arguing for applying it right then, and then forgot about it.

Hmph, now we're almost in beta period again. :-(.

> Blowing the dust off, it's attached. It fixes ArrayRef and RowExpr as
> well as ScalarArrayOpExpr, with a net growth of only 20 lines
> (largely comments).


>> On a side-note, I find it a bit awkward that ScalarArrayOpExpr uses a
>> 2-element List to hold the scalar and array arguments. Wouldn't it be
>> much more straightforward to have explicit "Expr *scalararg" and "Expr
>> *arrayarg" fields?
> I think it's modeled on OpExpr, which also uses a list though you could
> argue for separate leftarg and rightarg fields instead.

Yeah, I think that would be better for OpExpr, too. (For an unary
operator, rightarg would be unused.)

- Heikki

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