TAP information schema

[Patrick Dowler]

On 2007-10-11 16:05, Doug Tody wrote:
>> Pat wrote:
> > For the VOSpace example, if I was implementing that I would most
> > likely make vospace a database (for storage allocation purposes),
> > require authentication, and give each user implicit schema
> > creation privaledge. Then the uploaded VOtable would be known as
> > vospace.$user.$tableName and I would have to do minimal work to make
> > that happen and protect one user's tables from another.
>
> So what do you do with MySQL (and probably others) where there is
> only one catalog?  As we would like to be able to use ADQL to access
> both vospace tables and data tables in the same query, the only option
> (other than brute force copying tables) is to implement the vospace with
> a schema ("database" in MySQL).

Well, that is the issue - some people use one catalog and multiple schemata 
and others use multiple catalog and default or implicit (user) schemata. We 
have to accomodate both because both are in use and required in one system or 
another. What I meant was "if  I was implementing VOSpace on top of a db that 
supported multiple of each" (eg DB2 and sybase here). If it is MySQL 
underneath then the implementor has no choice but to use schemata to separate 
things (either a vospace schema and manually separate tables, or a bunch of 
schemata nominally managed by one VOSpace service. Either is doable. I just 
don't think we can have the TAP metadata dictate which one someone choses, so 
we have to ultimately (maybe not now) expose catalog, schema, and table 
concepts.

Anyway, I don't think we disagree. If this was the future ultra magic version 
of VOQL with XQueryMagic and ZOntologyMapper then we could hide stuff, but 
ADQL is mostly SQL and that means we can't hide stuff without being bitten 
later on. Anyone who wants to hide these details can do so by telling the 
user one thing (eg giving them unique table names) and re-writing the query 
to something else, but many arguments have been made that one should not have 
to do this and should in theory be able to more or less pass the query 
through with minor syntactic massaging. 

-- 

Patrick Dowler
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