VODataService

[Patrick Dowler]

On 2008-12-11 02:21:54 Gerard wrote:
> Supposing select-only is accepted. What do you see as the consequences?

I was seeing it more like a hint that using such a column in the where clause 
will not work as expected or not at all (the query will fail). That is always 
an option for the service if we don't add anything, but it is not a very good 
option.

> I suppose a select-only column transmits its select-only-ness to any
> expression it is part of.
> For example if it is the result in a sub-query, the wrapping query should
> not be allowed to use the result column, possibly changed, in a where
> clause eitehr.

I think that would follow and, as above, if the caller did something else it 
would at best not behave as expected. Also, if the query modified the URI 
somehow (it would nominally be type=char and arraysize=*) via string 
concatenation or substring() function calls, the result would be meaningless 
to everyone.

> Would you be allowed to ask
>   select distinct URL ...  ?

I think you could try, but the service may or may not be able to do it. In our 
case (column is a URI we convert on output) DISTINCT would work as expected.

> (of course I am just conservative, don't like change to things I thought I
> was familiar with)

Fair enough. I have not really thought through the implications and SQL allows 
for a lot of subtle ways to do things.

-- 

Patrick Dowler
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