Re: Qualified vs Unqualified calls (Was: Database server jobs and SQL tuning)

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

Hello John,

Interesting exercise.  I didn't bother to respond earlier even though I didn't 
believe 
the original premise.  I simply said "Bollocks" and discarded the note.  I'm 
feeling a 
little more loquacious this evening.  It only takes a little thought to 
disprove the 
premise.  The benchmark evidence is useful for substantiation.

It is true that a qualified call requires two resolutions: Resolve library then 
resolve object, therefore requiring the compiler or MI programmer to issue two 
calls 
to RSVLSP.
        1 - Resolve context
        2 - Use pointer to resolved context when resolving object

However a call to RSVLSP with no context information results in the name 
resolution 
list (what you know as the *LIBL) being searched linearly.  The NRL can contain 
15 
system libraries, 25 user libraries, 2 product libraries, and the current 
library, and 
even though the NRL contains resolved pointers (an array of 43 system 
pointers), 
resolving the actual object requires a call to RSLVSP for each entry in the NRL 
until 
the object is found -- in the worst case a total of 43 resolutions.

Note that the above is not true when resolving an object that can only exist in 
the 
machine context.  In that case a single resolution is performed.

Ergo, a qualified call is faster than an unqualified call when the NRL contains 
more 
than two contexts. Quod erat demonstrandum!

None of which has any bearing on whether qualified calls are a good idea or not!

Regards,
Simon Coulter.

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