Re: [PATCH] (DERBY-582) Dynamic parameter should be allowed to be the operand of unary operator "-". Derby throws exception 42X36: The '-' operator is not allowed to take a ? parameter as an operand."

[Mamta Satoor]

Hi Jeff,

 

I ran the test cases that you brought up with my very rough code changes and the code seems to handle them all correctly.

Here is what happens in each of the cases

 

   where t1.int_column + ? = - ?
The first parameter gets bound to the type of t1.int_column and then second parameter gets bound to the same type too.

 

   where t1.int_column = ? / - ?
This will not be accepted by Derby because both the operators for / are parameters. In fact, if you tried the same query but without the unary operator ie    where t1.int_column = ? / ?, Derby will throw an exception that both parameters around / can't be parameters.

 

where - ? not in (select t1.int_column + ? from . . .)
The second parameter gets the type of t1.int_column and then same type gets assigned to the first parameter.

 

thanks,

Mamta

 

On 9/28/05, Jeffrey Lichtman <[EMAIL PROTECTED]> wrote:

>I agree with your and Dan's point about possible precision loss. I
>am trying to find a way where rather than hard coding the -?/+? to
>Double, try to get it's datatype from the context where it is used.

There are circumstances where you can figure this out, but it's
ambiguous in the general case. For example:

   where t1.int_column + ? = - ?

Since both sides of the "=" operator have parameters, you can't use
the type of one side to figure out the type of the other side.

Here are some more examples of ambiguity:

   where t1.int_column = ? / - ?

   where - ? not in (select t1.int_column + ? from . . .)

I don't think it's a good idea to try to solve this problem at all.
There are a few cases where it's obvious what the type should be, and
many more where it's not. There's also an easy workaround (use the
CAST function). Even if we were able to figure out an algorithm to
determine the type of a parameter in all cases, would it be possible
to explain the behavior to an average user?


                       -        Jeff Lichtman
                                [EMAIL PROTECTED]
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