Hi Claus,
As described in http://docs.openlinksw.com/virtuoso/fn_exec.html, the "rows"
parameter is "An output array with one element per result row containing an
array with the leftmost column as element 0 and so forth".
Processing further the result can be done for ex. such as:
exec (,,,,, data);
for (declare i,l int, i := 0, l := length (data); i < l; i := i + 1)
{
-- do sth with for ex. with data[i][0],[i][1] etc.
}
Additionally, the example function "param_passing_demo" in
http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfsparqlinline
uses exec with SPARQL query.
Hope this helps.
Best Regards,
Rumi
----- Original Message -----
From: CStadler
To: virtuoso-users@lists.sourceforge.net
Sent: Tuesday, March 01, 2011 8:40 PM
Subject: [Virtuoso-users] Dump arbitrary query result as N-Triples
Hi,
So far I have used the script at the end of this mail for dumping a graph as
n-triples (basically its an adaption from
http://docs.openlinksw.com/virtuoso/rdfperformancetuning.html).
However now I want to adapt it so I can pass a string with graph-patterns in
order to be able to specify filters on what should be dumped.
The dump script I use contains the line:
for (select * from (sparql define input:storage "" select ?s ?p ?o { graph
`iri(?:srcgraph)` { ?s ?p ?o } } ) as sub option (loop)) do
I want to change it so it works with a dynamically created query, something
like:
str := sprintf ('sparql define input:storage "" select ?s ?p ?o { %s }',
myPattern)
myPattern could be something like "?s ?p ?o . ?s a Type . Filter(...)")
And this is where I am stuck now:
I can do exec(...) but then I don't know how I can iterate the result in the
for loop.
The doc at
http://docs.openlinksw.com/virtuoso/fn_exec.html
doens't give an example how to further process the result.
Alternatively, I thought I could use isql and do something like:
./isql 1111 dba dba "EXEC=Set Blobs On; Sparql define output:format 'NT'
Construct {?s ?p ?o .} From <http://mygraph.org> {?s ?p ?o .};"
However, first this ouputs additional lines for human readability and
therefore doesn't directly produce a valid rdf file (although it is possible to
cut the invalid heading and trailing lines away with head/tail, it is not a
very clean solution)
And second 'NT' is not a valid format (the docs don't mention it):
from http://docs.openlinksw.com/virtuoso/rdfsparql.html
"Supported values for output:format are RDF/XML and TURTLE (or TTL). If
both output:valmode and output:format are specified, output:format has higher
priority, raising an error if output:valmode is set to a value other than LONG.
"
Best regards,
Claus Stadler
For the sake of completeness here is the dump script I want to further adapt:
drop procedure dump_graph_nt;
create procedure dump_graph_nt(in srcgraph varchar, in out_file varchar, in
file_length_limit integer := -1)
{
declare file_name varchar;
declare env, ses any;
declare ses_len, max_ses_len, file_len, file_idx integer;
set isolation = 'uncommitted';
max_ses_len := 10000000;
file_len := 0;
file_idx := 1;
file_name := sprintf ('%s-%06d.nt', out_file, file_idx);
string_to_file (file_name || '.graph', srcgraph, -2);
env := vector (0, 0, 0);
ses := string_output ();
for (select * from (sparql define input:storage "" select ?s ?p ?o { graph
`iri(?:srcgraph)` { ?s ?p ?o } } ) as sub option (loop)) do
{
http_nt_triple (env, "s", "p", "o", ses);
ses_len := length (ses);
if (ses_len > max_ses_len)
{
file_len := file_len + ses_len;
if (file_length_limit >= 0 and file_len > file_length_limit)
{
string_to_file (file_name, ses, -1);
file_len := 0;
file_idx := file_idx + 1;
file_name := sprintf ('%s-%06d.nt', out_file, file_idx);
env := vector (0, 0, 0);
}
else
string_to_file (file_name, ses, -1);
ses := string_output ();
}
}
if (length (ses))
{
string_to_file (file_name, ses, -1);
}
};
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