Re: Different SPARQL execution order with recent Jena update (JENA-1813?)

[Andy Seaborne]

> I am still trying to narrow down what has changed
It may be JENA-1813 - being about optimziation, the details of the real 
case probably matter. Let us know what you discover.

JENA-1813 fixed a specific problem caused by the BIND inside the GRAPH 
("AS ?dummy" - not the outer one).  If the inside is a different pattern 
it seems optimize properly if I understand the details. Maybe some small 
rewrite will work in the real case.

There is a follow-up (open) JENA-1815 as well.

Question: was this change intentional and is this behavior going to stay 
in Jena? If it does stay, how can I switch it off?

The first algebra expression below is the translation of the query and 
what is executing now some optimization doesn't get applied. It is the 
right answers.

    Andy

On 29/01/2020 05:08, Holger Knublauch wrote:
Hi,

on a branch of our product we have upgraded to jena 3.14 (due to the 
Thrift issue). Since then various SPARQL queries have stopped working. 
Of particular concern appears to be the evaluation of GRAPH ?graph 
clauses where ?graph is determined by a BIND. I am still trying to 
narrow down what has changed but suspect it's due to

https://issues.apache.org/jira/browse/JENA-1813

Here is an example query - a simplified version derived from a query in 
the product:

SELECT *
WHERE {
     BIND(<http://topbraid.org/teamwork#teamGraph>($this) AS ?teamGraph)
     GRAPH ?teamGraph {
         BIND (42 AS ?dummy)
     }
}

which is executed with $this prebound to a graph resource (e.g. 
<urn:x-evn-master:geo>). In 3.14 this seems to produce the following 
algebra:

(join
   (extend ((?teamGraph (<http://topbraid.org/teamwork#teamGraph> ?this)))
     (table unit))
   (graph ?teamGraph
     (extend ((?dummy 42))
       (table unit))))

while in 3.13.1 it produces

(sequence
   (extend ((?teamGraph (teamwork:teamGraph ?this)))
     (table unit))
   (graph ?teamGraph
     (extend ((?dummy 42))
       (table unit))))

As a result, the new version enters the GRAPH ?teamGraph with unbound 
?teamGraph and thus iterates over all graphs which is not working for 
our platform:

If my observations so far are correct then this change to Jena would 
have quite deep consequences and break not just our own queries but also 
those written by customers. We will likely have to roll back to a 
previous Jena version for the upcoming release of our product.

Question: was this change intentional and is this behavior going to stay 
in Jena? If it does stay, how can I switch it off?

Thanks
Holger