[TAP] case sensitivity of query -- schema names

[Patrick Dowler]

* summary of where we are with respect to case of catalog, schema, table, and 
column names:

- the current draft doesn't really commit, but says clients should preserve 
the case of these names (as found in the metadata); I don't see any reason 
this won't work, but it is a rule/complexity for clients

- if TAP is not case sensitive AND the back end DB is case sensitive with 
respect to these names, the services would need to parse the query to find 
all references and map them to the correct internal names

- ADQL specifies that these names are not case sensitive; some RDBMS 
implementations are case sensitive

- TAP could be used with other query languages with different rules w.r.t. 
case

* an observation:

I have seen some claims that implementing an ADQL parser to map the table and 
column names would be very difficult. It appears that these claims are coming 
from people who have not done such an implementation, while those that have 
seem to think it wasn't that hard after all*.  So, all the evidence is to the 
contrary: it is not that hard to parse the ADQL and map the names to the 
correct internal names.

I would also note that as far as ADQL parsing goes, mapping tables names is 
the easy one: the region functions can be much harder (depending on your DB 
schema). It has been said many times that we are really misleading people if 
we imply that they can implement TAP+ADQL on anything but a real relational 
database. Along the same lines and given how devious SQL is, I no longer 
think it is plausible to implement without an ADQL parser except maybe in the 
simplest case or if the implementor is quite lucky -- but I also don't think 
this is much of a technical barrier.

* That was in fact my own experience: I thought it would be hard, found out 
that SQL was even more devious than I thought, and yet this particular 
problem can be solved pretty easily (as I described the other day). 

-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2M7

Centre canadien de donnees astronomiques
Conseil national de recherches Canada
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Victoria (C.-B.) V9E 2M7