Re: [Tarantool-patches] [PATCH v2 1/1] sql: make NUMBER to be union of SQL numeric types

[Nikita Pettik <korablev@tarantool.org>]

On 31 Dec 12:46, Mergen Imeev wrote:
> Hi! Thank you for review. My answer below.
> 
> On Tue, Dec 31, 2019 at 10:56:07AM +0200, Nikita Pettik wrote:
> > On 31 Dec 11:50, imeevma@tarantool.org wrote:
> > > This patch makes number to be union of UNSIGNED, INTEGER and
> > > DOUBLE numeric types.
> > > 
> > > Closes #4233
> > > Closes #4463
> > 
> > Please, explain in details changes in explicit/implicit
> > casts behaviour.
> > 
> Fixed:
> 
> commit 492646da4f781b863e5e3e488a0be53f31d28964
> Author: Mergen Imeev <imeevma@gmail.com>
> Date:   Sat Oct 26 17:27:53 2019 +0300
> 
>     sql: make NUMBER to be union of SQL numeric types
>     
>     This patch makes number to be union of UNSIGNED, INTEGER and
>     DOUBLE numeric types.
>     
>     Closes #4233
>     Closes #4463
>     
>     @TarantoolBot document
>     Title: NUMBER type in SQL.

Could you please intead of 3 paragraphs just include following
changelog list:

"This patch makes definition of NUMBER type be consistent with NoSQL.
 Previously (for historic reasons) in half-cases NUMBER served as a
 synonym of DOUBLE type.
 After patch is applied following will change:
 - CAST AS NUMBER operation no more longer results in any value
   change in case value is already of numeric type. Example:
   Obsolete behaviour:
	SELECT CAST(922337206854774800 AS NUMBER);
        Result: 9223372036854774784
   New behaviour:
        SELECT CAST(922337206854774800 AS NUMBER);                              
        Result: 9223372036854774800LL
 - ...
"

Or group implicit/explicit cast changes. Text below is quite
compicated to perceive (IMHO).

>     
>     The NUMBER type in SQL is the union of all currently available
>     numeric types in SQL: INTEGER, UNSIGNED, and DOUBLE. The types
>     INTEGER and DOUBLE can be called subtypes of type NUMBER. Any
>     value of type NUMBER has a subtype of INTEGER or DOUBLE. When
>     any numeric value is implicitly or explicitly casted to NUMBER,
>     the only thing that can change is its type. Its type will become
>     NUMBER. When a value of type NUMBER is cast explicitly or
>     implicitly to other numeric types, the rules applicable to the
>     cast are determined by the subtype of the value.
>     
>     If a value of type STRING can be implicitly cast to value of
>     type INTEGER or DOUBLE, then this value can be cast explicitly
>     and implicitly to a value of type NUMBER. If this value can be
>     implicitly cast to INTEGER, then its subtype will be INTEGER.
>     The subtype will be DOUBLE in another case.
>     
>     If a value of type VARBINARY can be explicitly cast to type
>     INTEGER or DOUBLE, then this value can be explicitly cast to a
>     value of type NUMBER. If this value can be explicitly cast to
>     INTEGER, then its subtype will be INTEGER. The subtype will be
>     DOUBLE in another case.
> > > ---