Thread: Problem in ExecEvalExpr function

Hi,

I have some doubts related to ExecEvalExpr functions which is used to 
executing the expression.

Here we are finding the subexpression recursively.
But I am not able to find it out that where exactly the comparison taking 
place.
For eg.
relation A
id   name   age
relation B
name age status

if query is
select id , name , age , status from A , B where A.name = B.name and A.age 
= B.age.

Then parser find this "and" condition and divide this into two expression.
But I am not getting in which function exactly these comparison between 
tupleslot taking place.

-- 
------------------
| Sandeep Satpal |
| M.Tech Student |
| Lab 212 KReSIT |
------------------

On Tue, Oct 18, 2005 at 02:38:39PM +0530, sandeep satpal wrote:
>
> Hi,
>
> I have some doubts related to ExecEvalExpr functions which is used to
> executing the expression.

Since they are operators, they go through ExecEvalOper. However, after
the first call they go through ExecMakeFunctionResult. The operator has
an oid which is used to find the function and it is eventually called
using FunctionCallInvoke.

Note, ExecEvalExpr is a macro, so you can't break on it.

> Here we are finding the subexpression recursively.
> But I am not able to find it out that where exactly the comparison taking
> place.
> For eg.
> relation A
> id   name   age
> relation B
> name age status
>
> if query is
> select id , name , age , status from A , B where A.name = B.name and A.age
> = B.age.

Note that if the operator appears in the OPERATOR CLASS and the
optimizer has determined that it can use an index, it won't go through
this code at all, instead using the compare function in _bt_compare.

> Then parser find this "and" condition and divide this into two expression.
> But I am not getting in which function exactly these comparison between
> tupleslot taking place.

FunctionCallInvoke will be calling the function for operator =.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.

Sandeep,

You seem to be having a lot of trouble understanding the evaluation code which isn't that complex.  Are you still trying to do that case-insensitive comparison?  If so, I seriously recommend that you just look at the citext project on gborg and stop messing around in the backend, it's just going to get ya into trouble.





--
Respectfully,

Jonah H. Harris, Database Internals Architect
EnterpriseDB Corporation
http://www.enterprisedb.com/