Hello Sebastian,
Consider this:
create procedure nrl_drop_graphs(in query_base varchar, in query_params
any := null)
{
declare stat, msg varchar;
declare metas, rset any;
stat := '00000';
if (query_params is null)
query_params := vector ();
exec ('sparql ' || query_base, stat, msg, query_params, 1000, metas,
rset);
if ('00000' <> stat) -- If error state is set while the query is
executed...
signal (stat, msg); -- ...then we resignal it.
if (1 <> length (metas[0]))
signal ('?????', 'The query is supposed to return exactly one
column, containing graphs to drop');
foreach (any row in rset) do
{
declare g any;
g := row[0]; -- The value of first (and the only) columns of row.
if (__tag(g) in (__tag of varchar, __tag of nvarchar, __tag of
IRI_ID))
{
sparql drop silent graph identified by iri(?:g);
commit work;
}
else
signal ('?????', 'Invalid graph IRI');
}
}
;
A basic test is:
sparql insert in graph <http://test1/> { <s1> <test> <o1> };
sparql insert in graph <http://test2/> { <s2> <test> <o2> };
sparql insert in graph <http://test3/> { <s2> <test> <o3> };
sparql select * where { graph ?g { ?s <test> ?o} };
--- Should return three rows.
nrl_drop_graphs ('select ?g where { graph ?g { ?s <test> ?o }}');
sparql select * where { graph ?g { ?s <test> ?o} };
--- Should return zero rows because graphs are just dropped.
Best Regards,
Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com
On Wed, 2011-11-23 at 21:04 +0100, Sebastian Trüg wrote:
> Hello list,
>
> I am trying to write a stored procedure which deletes a set of graphs
> matching a query. This is what I have so far:
>
> create procedure nrl_drop_graphs(IN QUERY_BASE STRING)
> {
> DECLARE query STRING;
> query := query_base + ' LIMIT 1000';
>
> declare cnt integer;
> cnt := 0;
>
> while(1)
> {
> declare it cursor for sparql query;
> open it;
> declare v any;
> while(1)
> {
> WHENEVER NOT FOUND goto done;
> FETCH it INTO g;
> vector_concat(v, g);
> }
> done: ;
> close it;
>
> if(length(v)=0) return;
>
> for(any g in v)
> {
> cnt := cnt + 1;
> sparql drop graph g;
> }
> }
> }
>
> The idea is to get all the graphs in batches of 1000 and drop them one
> by one since that is not possible with SPARUL (at least not in 6.1.4).
>
> It fails at the "declare cursor" since it is not happy with the
> "sparql". This is the first time I try my luck with stored procedures so
> the code may contains lots of stupidities. :P
>
> Thanks for your help.
>
> Cheers,
> Sebastian
>
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