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From: Imeev Mergen <imeevma@tarantool.org>
To: Peter Gulutzan <pgulutzan@ocelot.ca>,
	tarantool-discussions@dev.tarantool.org, kostja.osipov@gmail.com,
	korablev@tarantool.org, alexander.turenko@tarantool.org,
	v.shpilevoy@tarantool.org, kyukhin@tarantool.org,
	tsafin@tarantool.org
Subject: Re: [Tarantool-discussions] Implicit cast for ASSIGNMENT
Date: Thu, 30 Apr 2020 18:10:14 +0300
Message-ID: <37b646d1-39a3-f39a-c436-f315fe1359a0@tarantool.org> (raw)
In-Reply-To: <e2d9ebaf-2609-d304-b4dd-debc779af2a8@ocelot.ca>

Hi,

On 4/30/20 5:40 PM, Peter Gulutzan wrote:
> Hi,
>
> Going back to your original question:
>
> On 2020-04-30 6:04 a.m., Imeev Mergen wrote:
> > Hi! Here we go again. Last time we have not come to a colclusion.
> >
> > So, I suggest these rules for implicit cast for ASSIGNMENT:
> > 1) Any value can be implicitly cast to ANY type.
> This is not supported in SQL yet, I have expected that
> casting a scalar value to ANY would be like casting to SCALAR.
True.

> > 2) Any scalar values ​​can be implicitly cast to SCALAR type.
> I am not sure what this means.
> TYPEOF(CAST(1 AS SCALAR)) is not 'scalar', it is 'integer'.
> That is, we allow the syntax for an explicit cast, but do nothing.
> So, if all you are saying is that
> "we allow implicit cast, but do nothing"
> then there is no reason to object, there is no behaviour change.
No, I plan to fix it. I already have a fix, and I plan to push it
among the patches for this problem.

> > 3) Values ​​of numeric types can be implicitly cast to other numeric
> > types.
> I believe this but K. Yukhin decided to close issue#4216.
> > 4) Implicit casting is prohibited, except as described above.
> Yes, "here we go again".
> My opinion is unchanged:
> Implicit cast of string to number was a mistake.
> All comparison of values of different data types should be legal.
Not sure if we should discuss comparison here, however, do you
mean that we should allow comparison of values ​​of different types
without implicit casting? Using scalar rules?

> Of course, assignment may cause an out-of-range error.
> >
> >
> > I think that the rules for implicit casting when assigning value
> > of numeric type must be the same as in C.
> >
> You mean there should be truncation not rounding?
Yes.

> > On 2/13/20 5:25 PM, Mergen Imeev wrote:
> >> Hi all,
> >> I would like to discuss the second issue of casts in SQL. I mean
> >> implicit casting for ASSIGNMENT.
> >>
> >> For now, I suggest avoiding questions about SCALAR, as the
> >> discussion is already in progress.
> >>
> >> So, I suggest removing the current implicit casts. We can
> >> reimplement implicit casts in accordance with ANSI in issue #3836.
> >> But since priority of #3836 is low, this is most likely not going
> >> to happen for some time.
> >>
> >> At the moment, I see two ways to remove implicit casts:
> >> 1) Disable all implicit casts, except casts for numeric values.
> >> These casts will become UDCF later.
> >> 2) Disable all implicit casts. Assignment in Tarantool-SQL will
> >> work the same as in noSQL Tarantool.
> >>
> >> What do you think about this?
> >>
> For this earlier email, didn't everyone respond already?
I'd like to get more definite answers.

>
> Peter Gulutzan
>

  reply	other threads:[~2020-04-30 15:10 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13 14:25 Mergen Imeev
2020-02-13 14:40 ` Konstantin Osipov
2020-02-13 22:20 ` Peter Gulutzan
2020-04-30 12:04 ` Imeev Mergen
2020-04-30 12:35   ` Konstantin Osipov
2020-04-30 12:56     ` Imeev Mergen
2020-04-30 13:09       ` Konstantin Osipov
2020-04-30 13:12         ` Imeev Mergen
2020-04-30 14:04           ` Konstantin Osipov
2020-04-30 14:15             ` Peter Gulutzan
2020-04-30 14:28               ` Konstantin Osipov
2020-04-30 14:40   ` Peter Gulutzan
2020-04-30 15:10     ` Imeev Mergen [this message]
2020-04-30 16:04       ` Peter Gulutzan
2020-05-07 16:14         ` Peter Gulutzan
2020-05-08 11:57           ` Kirill Yukhin
2020-04-30 22:52       ` [Tarantool-discussions] Descriptive SQL Style Guide Peter Gulutzan

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