[tarantool-patches] Re: [PATCH 4/6] sql: make built-in functions operate on unsigned values

["n.pettik" <korablev@tarantool.org>]

> On 2 Jul 2019, at 00:53, Vladislav Shpilevoy <v.shpilevoy@tarantool.org> wrote:
> Thanks for the fixes!
> On 01/07/2019 16:21, n.pettik wrote:
>> 
>>>> diff --git a/src/box/sql/func.c b/src/box/sql/func.c
>>>> index 457c9b92b..365f8f9d2 100644
>>>> --- a/src/box/sql/func.c
>>>> +++ b/src/box/sql/func.c
>>>> @@ -645,21 +638,13 @@ ICU_CASE_CONVERT(Upper);
>>>> static void
>>>> randomFunc(sql_context * context, int NotUsed, sql_value ** NotUsed2)
>>>> {
>>>> -	sql_int64 r;
>>>> +	int64_t r;
>>>> 	UNUSED_PARAMETER2(NotUsed, NotUsed2);
>>>> 	sql_randomness(sizeof(r), &r);
>>>> -	if (r < 0) {
>>>> -		/* We need to prevent a random number of 0x8000000000000000
>>>> -		 * (or -9223372036854775808) since when you do abs() of that
>>>> -		 * number of you get the same value back again.  To do this
>>>> -		 * in a way that is testable, mask the sign bit off of negative
>>>> -		 * values, resulting in a positive value.  Then take the
>>>> -		 * 2s complement of that positive value.  The end result can
>>>> -		 * therefore be no less than -9223372036854775807.
>>>> -		 */
>>>> -		r = -(r & LARGEST_INT64);
>>>> -	}
>>>> -	sql_result_int64(context, r);
>>>> +	if (r < 0)
>>>> +		sql_result_int(context, r);
>>>> +	else
>>>> +		sql_result_uint(context, r);
>>> 
>>> 1. To avoid such mess I propose you the same as for mem_set_int - make
>>> several functions:
>> 
>> What kind of mess do you mean? Here we have two functions:
>> one sets unsigned result, another one - signed. Pretty straight
>> approach, isn’t it? What is more, this is the only place where
>> branching is required.
> 
> If it is so straight, then why do you need branching at all?
> I see, that sql_result_int() calls mem_set_i64, which is able
> to take positive values.
> 
> I've done this and the tests passed. Why?

You had already answered your question:

> I see, that sql_result_int() calls mem_set_i64, which is able
> to take positive values.

Anyway sql_randomness() doesn’t return sign of random number.
So actually, your diff is completely correct and I’ve applied it.

> @@ -621,10 +621,7 @@ randomFunc(sql_context * context, int NotUsed, sql_value ** NotUsed2)
> 	int64_t r;
> 	UNUSED_PARAMETER2(NotUsed, NotUsed2);
> 	sql_randomness(sizeof(r), &r);
> -	if (r < 0)
> -		sql_result_int(context, r);
> -	else
> -		sql_result_uint(context, r);
> +	sql_result_int(context, r);
> }
> 
>> 
>>>   /* Return an int64 value, sign is detected inside. */
>>>   sql_result_i64(int64_t value);
>>> 
>>>   /* Return a uint64 value. */
>>>   sql_result_u64(uint64_t value);
>>> 
>>>   /* Return an integer value with explicit sign. */
>>>   sql_result_int(int64_t value, bool is_negative);
>>> 
>>>> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
>>>> index c0e2ab699..4697e3003 100644
>>>> --- a/src/box/sql/sqlInt.h
>>>> +++ b/src/box/sql/sqlInt.h
>>>> @@ -455,6 +455,9 @@ sql_column_subtype(struct sql_stmt *stmt, int i);
>>>> sql_int64
>>>> sql_value_int64(sql_value *);
>>>> 
>>>> +uint64_t
>>>> +sql_value_uint64(sql_value *val);
>>>> +
>>>> const unsigned char *
>>>> sql_value_text(sql_value *);
>>>> 
>>>> @@ -496,13 +499,13 @@ void
>>>> sql_result_error_code(sql_context *, int);
>>>> 
>>>> void
>>>> -sql_result_int(sql_context *, int);
>>>> +sql_result_int(sql_context *, int64_t);
>>>> 
>>>> void
>>>> -sql_result_bool(struct sql_context *ctx, bool value);
>>>> +sql_result_uint(sql_context *ctx, int64_t u_val);
>>> 
>>> 2. Why result_uint takes int instead of uint?
>> 
>> Because mem_set_int() accepts int64 and to avoid
>> extra casts to uint (since almost al used values are singed).
> 
> This function has nothing to do with mem_set_int().
> This function calls mem_set_u64(), and its argument is
> unsigned. So what is a problem, again?

Sorry, answered before I introduced mem_set_u64().
Now there’s no problem:

diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
index 088cfbc51..976b4486a 100644
--- a/src/box/sql/sqlInt.h
+++ b/src/box/sql/sqlInt.h
@@ -398,7 +398,7 @@ void
 sql_result_double(sql_context *, double);
 
 void
-sql_result_uint(sql_context *ctx, int64_t u_val);
+sql_result_uint(sql_context *ctx, uint64_t u_val);
 
 void
 sql_result_int(sql_context *, int64_t);
diff --git a/src/box/sql/vdbeapi.c b/src/box/sql/vdbeapi.c
index 2b1115074..ff7ce658b 100644
--- a/src/box/sql/vdbeapi.c
+++ b/src/box/sql/vdbeapi.c
@@ -330,7 +330,7 @@ sql_result_double(sql_context * pCtx, double rVal)
 }
 
 void
-sql_result_uint(sql_context *ctx, int64_t u_val)
+sql_result_uint(sql_context *ctx, uint64_t u_val)
 {
        mem_set_u64(ctx->pOut, u_val);
 }