[tarantool-patches] Re: [PATCH 6/6] sql: allow to specify UNSIGNED column type

[n.pettik]

> On 18 Jul 2019, at 23:18, Vladislav Shpilevoy <v.shpilevoy at tarantool.org> wrote:
> 
> Hi!
> 
> Thanks for the fixes!
> 
>>> -------------------------
>>> vdbe.c:307
>>> 
>>>> 	case FIELD_TYPE_INTEGER:
>>>> 	case FIELD_TYPE_UNSIGNED:
>>>> 		if ((record->flags & MEM_Int) == MEM_Int)
>>>> 			return 0;
>>>> 		if ((record->flags & MEM_UInt) == MEM_UInt)
>>>> 			return 0;
>>>> 		if ((record->flags & MEM_Real) == MEM_Real) {
>>>> 			int64_t i = (int64_t) record->u.r;
>>>> 			if (i == record->u.r)
>>>> 				mem_set_int(record, record->u.r,
>>>> 					    record->u.r <= -1);
>>>> 			return 0;
>>>> 		}
>>> 
>>> It is a part of function mem_apply_type. When target type is
>>> UNSIGNED, and a value is MEM_Int, you do nothing. Why? Looks like
>>> it is possible to pass here a negative value, and CAST UNSIGNED
>>> would do nothing.
>> 
>> Basically, this function implements sort of implicit cast
>> which takes place before comparison/assignment.
>> For comparisons it makes no sense - we can compare
>> integer with unsigned value - the latter is always greater.
>> For assignment it is also meaningless: if we attempt
>> at inserting negative values to unsigned field appropriate
>> error will be raised anyway. If you can come up with
>> specific example, let’s discuss it.
>> 
> 
> I can't provide a test. But the function is named mem_apply_type,
> and it doesn't apply type, when it is unsigned, and a value is
> negative. Doesn't it look wrong to you?
> 
> If some code wants to get an integer, it can apply FIELD_TYPE_INTEGER
> instead of FIELD_TYPE_UNSIGNED. IMO, an attempt to apply unsigned
> to int should raise an error here. Otherwise this function can't
> be named 'apply_type' because it ignores negative -> unsigned case.

Okay, let’s rename it. I can suggest these options:

mem_cast_implicit()
mem_cast_implicit_to_type()
mem_implicit_cast_to_type()
mem_convert_implicit()
mem_convert_to_type()
mem_type_coerce_implicit()
mem_type_implicit_coercion()
mem_type_coercion_implicit()
mem_implicit_type_juggling()
mem_implicit_juggle_to_type()
mem_do_implicit_conversion()
mem_do_implicit_coercion()

Or any other combination :)

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