Hello Alexander,
You may use sequence_next()
(http://docs.openlinksw.com/virtuoso/fn_sequence_next.html) BIF as
source of autoincremented integers.
However this function should be used with care in SPARUL statements as
well as in UPDATE SQL statement. The optimizer does not know that the
function returns new value every time so it may decide to call it once
at the beginning of the query run and reuse the result. That may not
match your intention if you manipulate a batch of different rows in a
single request. To fool the optimizer, pass fake third argument to the
function such as a primary key of the updated row or fields of inserted
rows or the like, i.e. something that obviously can not be calculated in
advance. The function will ignore them but the optimizer will be fooled
in a desired way.
To construct sequential IRIs, the popular trick is
IRI(bif:sprintf('...%d...', bif:sequence_next ('mysequence',
1, ?some_variable_from_select)))
Wrap an expression like this in backquotes and use in constructor
template instead of a plain variable, that's all.
Note that bif:sprintf should form an absolute IRI as namespace prefixes
and BASE will not play any role at the runtime.
Best Regards,
Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com
On Fri, 2010-02-26 at 11:54 +0100, Alexander Sidorov wrote:
> Hello!
>
> What is the preferred way of stroring autoincrement values in
> RDF-storage? Now I just use GUIDs (but don't like them) and have some
> workaround ideas of using relational table's autoincrement field
> values at RDF-storage. But may be there is some build-in support?
>
> Regards,
> Alexander
