[
https://issues.apache.org/jira/browse/JENA-1128?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Osma Suominen updated JENA-1128:
--------------------------------
Description:
I'm running a SPARQL query against a SDB loaded with SKOS data. The intent of
the query is to check for broken links, i.e. skos:closeMatch relationships that
point to nonexistent concepts in another SKOS dataset. I have simplified my
query to a rather minimal test case below. In this case, also the remote data
is included in the same graph for simplicity.
Here is my test data:
{noformat}
@prefix skos: <http://www.w3.org/2004/02/skos/core#>.
@prefix local: <http://example.com/local/>.
@prefix remote: <http://example.com/remote/>.
local:conceptA a skos:Concept ;
skos:prefLabel "Local concept A"@en ;
skos:note "has a valid link to an existing remote concept" ;
skos:closeMatch remote:conceptC .
local:conceptB a skos:Concept ;
skos:prefLabel "Local concept B"@en ;
skos:note "has a broken link to a nonexistent remote concept" ;
skos:closeMatch remote:conceptD .
remote:conceptC a skos:Concept ;
skos:prefLabel "Remote concept C"@en .
{noformat}
This is my SPARQL query:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT * WHERE {
?local skos:closeMatch ?remote .
MINUS { ?remote a skos:Concept }
}
{noformat}
If I run the query using the command line tool "sparql" from the apache-jena
distribution, it returns the correct result, i.e. the one concept with the
broken link:
{noformat}
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
But when I load the above data into a SDB database (MySQL) and use sdbquery
with the same SPARQL query, I get a different result (here run with the --debug
option) which has an extra row:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE
{ ?local skos:closeMatch ?remote
MINUS
{ ?remote a skos:Concept }
}
- - - - - - - - - - - - - -
SELECT -- V_3=?remote
R_3.lex AS V_3_lex, R_3.datatype AS V_3_datatype, R_3.lang AS V_3_lang,
R_3.type AS V_3_type
FROM
( SELECT -- ?remote:(T_2.s=>T_2.X_1)
T_2.s AS X_1
FROM Triples AS T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_2.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_2.o = 1728757386496985884 -- Const: skos:Concept
)
) AS T_2 -- ?remote:(T_2.s=>T_2.X_1)
LEFT OUTER JOIN
Nodes AS R_3 -- Var: ?remote
ON ( T_2.X_1 = R_3.hash )
(minus
(SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
R_1.type/V_1_type
R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
R_2.type/V_2_type
Join/left outer
Join/left outer
SqlSelectBlock/T_1
T_1.p = 2699241716664962559
Table T_1 -- ?local skos:closeMatch ?remote
Table R_1 -- Var: ?local
Condition T_1.s = R_1.hash
Table R_2 -- Var: ?remote
Condition T_1.o = R_2.hash''')
(SQL '''SqlSelectBlock/S_2 -- V_3=?remote
R_3.lex/V_3_lex R_3.datatype/V_3_datatype R_3.lang/V_3_lang
R_3.type/V_3_type
Join/left outer
SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
T_2.s/X_1
T_2.p = -6430697865200335348
T_2.o = 1728757386496985884
Table T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
Table R_3 -- Var: ?remote
Condition T_2.X_1 = R_3.hash''')
)
SELECT -- V_1=?local V_2=?remote
R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
R_1.type AS V_1_type,
R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
R_2.type AS V_2_type
FROM
( SELECT *
FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
)
) AS T_1
LEFT OUTER JOIN
Nodes AS R_1 -- Var: ?local
ON ( T_1.s = R_1.hash )
LEFT OUTER JOIN
Nodes AS R_2 -- Var: ?remote
ON ( T_1.o = R_2.hash )
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptA> | <http://example.com/remote/conceptC> |
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
If I change the query to use FILTER NOT EXISTS instead of MINUS, then I get the
correct result also with sdbquery:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE
{ ?local skos:closeMatch ?remote
FILTER NOT EXISTS { ?remote a skos:Concept }
}
- - - - - - - - - - - - - -
(filter (notexists
(SQL '''SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
T_2.s/X_1
T_2.p = -6430697865200335348
T_2.o = 1728757386496985884
Table T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept''')
)
(SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
R_1.type/V_1_type
R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
R_2.type/V_2_type
Join/left outer
Join/left outer
SqlSelectBlock/T_1
T_1.p = 2699241716664962559
Table T_1 -- ?local skos:closeMatch ?remote
Table R_1 -- Var: ?local
Condition T_1.s = R_1.hash
Table R_2 -- Var: ?remote
Condition T_1.o = R_2.hash''')
)
SELECT -- V_1=?local V_2=?remote
R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
R_1.type AS V_1_type,
R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
R_2.type AS V_2_type
FROM
( SELECT *
FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
)
) AS T_1
LEFT OUTER JOIN
Nodes AS R_1 -- Var: ?local
ON ( T_1.s = R_1.hash )
LEFT OUTER JOIN
Nodes AS R_2 -- Var: ?remote
ON ( T_1.o = R_2.hash )
SELECT *
FROM Triples AS T_3 --
<http://example.com/remote/conceptC>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_3.s = 5972767169237582230 -- Const:
<http://example.com/remote/conceptC>
AND T_3.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_3.o = 1728757386496985884 -- Const: skos:Concept
)
SELECT *
FROM Triples AS T_4 --
<http://example.com/remote/conceptD>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_4.s = 8175828786801660008 -- Const:
<http://example.com/remote/conceptD>
AND T_4.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_4.o = 1728757386496985884 -- Const: skos:Concept
)
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
However, in my actual query that this example is based on
(https://github.com/NatLibFi/Finto-data/blob/master/tools/yso-updater-sparql/5-ysa-removed-concepts.rq)
using FILTER NOT EXISTS is not an efficient solution, because the subtracted
part uses a federated query and it will result in almost 30000 queries to be
performed to the remote endpoint instead of just one.
I'm using the most recent snapshots available from repository.apache.org.
was:
I'm running a SPARQL query against a SDB loaded with SKOS data. The intent of
the query is to check for broken links, i.e. skos:closeMatch relationships that
point to nonexistent concepts in another SKOS dataset. I have simplified my
query to a rather minimal test case below. In this case, also the remote data
is included in the same graph for simplicity.
Here is my test data:
{noformat}
@prefix skos: <http://www.w3.org/2004/02/skos/core#>.
@prefix local: <http://example.com/local/>.
@prefix remote: <http://example.com/remote/>.
local:conceptA a skos:Concept ;
skos:prefLabel "Local concept A"@en ;
skos:note "has a valid link to an existing remote concept" ;
skos:closeMatch remote:conceptC .
local:conceptB a skos:Concept ;
skos:prefLabel "Local concept B"@en ;
skos:note "has a broken link to a nonexistent remote concept" ;
skos:closeMatch remote:conceptD .
remote:conceptC a skos:Concept ;
skos:prefLabel "Remote concept C"@en .
{noformat}
This is my SPARQL query:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT * WHERE {
?local skos:closeMatch ?remote .
FILTER NOT EXISTS { ?remote a skos:Concept }
}
{noformat}
If I run the query using the command line tool "sparql" from the apache-jena
distribution, it returns the correct result, i.e. the one concept with the
broken link:
{noformat}
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
But when I load the above data into a SDB database (MySQL) and use sdbquery
with the same SPARQL query, I get a different result (here run with the --debug
option) which has an extra row:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE
{ ?local skos:closeMatch ?remote
MINUS
{ ?remote a skos:Concept }
}
- - - - - - - - - - - - - -
SELECT -- V_3=?remote
R_3.lex AS V_3_lex, R_3.datatype AS V_3_datatype, R_3.lang AS V_3_lang,
R_3.type AS V_3_type
FROM
( SELECT -- ?remote:(T_2.s=>T_2.X_1)
T_2.s AS X_1
FROM Triples AS T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_2.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_2.o = 1728757386496985884 -- Const: skos:Concept
)
) AS T_2 -- ?remote:(T_2.s=>T_2.X_1)
LEFT OUTER JOIN
Nodes AS R_3 -- Var: ?remote
ON ( T_2.X_1 = R_3.hash )
(minus
(SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
R_1.type/V_1_type
R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
R_2.type/V_2_type
Join/left outer
Join/left outer
SqlSelectBlock/T_1
T_1.p = 2699241716664962559
Table T_1 -- ?local skos:closeMatch ?remote
Table R_1 -- Var: ?local
Condition T_1.s = R_1.hash
Table R_2 -- Var: ?remote
Condition T_1.o = R_2.hash''')
(SQL '''SqlSelectBlock/S_2 -- V_3=?remote
R_3.lex/V_3_lex R_3.datatype/V_3_datatype R_3.lang/V_3_lang
R_3.type/V_3_type
Join/left outer
SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
T_2.s/X_1
T_2.p = -6430697865200335348
T_2.o = 1728757386496985884
Table T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
Table R_3 -- Var: ?remote
Condition T_2.X_1 = R_3.hash''')
)
SELECT -- V_1=?local V_2=?remote
R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
R_1.type AS V_1_type,
R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
R_2.type AS V_2_type
FROM
( SELECT *
FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
)
) AS T_1
LEFT OUTER JOIN
Nodes AS R_1 -- Var: ?local
ON ( T_1.s = R_1.hash )
LEFT OUTER JOIN
Nodes AS R_2 -- Var: ?remote
ON ( T_1.o = R_2.hash )
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptA> | <http://example.com/remote/conceptC> |
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
If I change the query to use FILTER NOT EXISTS instead of MINUS, then I get the
correct result also with sdbquery:
{noformat}
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE
{ ?local skos:closeMatch ?remote
FILTER NOT EXISTS { ?remote a skos:Concept }
}
- - - - - - - - - - - - - -
(filter (notexists
(SQL '''SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
T_2.s/X_1
T_2.p = -6430697865200335348
T_2.o = 1728757386496985884
Table T_2 -- ?remote
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept''')
)
(SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
R_1.type/V_1_type
R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
R_2.type/V_2_type
Join/left outer
Join/left outer
SqlSelectBlock/T_1
T_1.p = 2699241716664962559
Table T_1 -- ?local skos:closeMatch ?remote
Table R_1 -- Var: ?local
Condition T_1.s = R_1.hash
Table R_2 -- Var: ?remote
Condition T_1.o = R_2.hash''')
)
SELECT -- V_1=?local V_2=?remote
R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
R_1.type AS V_1_type,
R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
R_2.type AS V_2_type
FROM
( SELECT *
FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
)
) AS T_1
LEFT OUTER JOIN
Nodes AS R_1 -- Var: ?local
ON ( T_1.s = R_1.hash )
LEFT OUTER JOIN
Nodes AS R_2 -- Var: ?remote
ON ( T_1.o = R_2.hash )
SELECT *
FROM Triples AS T_3 --
<http://example.com/remote/conceptC>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_3.s = 5972767169237582230 -- Const:
<http://example.com/remote/conceptC>
AND T_3.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_3.o = 1728757386496985884 -- Const: skos:Concept
)
SELECT *
FROM Triples AS T_4 --
<http://example.com/remote/conceptD>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
WHERE ( T_4.s = 8175828786801660008 -- Const:
<http://example.com/remote/conceptD>
AND T_4.p = -6430697865200335348 -- Const:
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
AND T_4.o = 1728757386496985884 -- Const: skos:Concept
)
------------------------------------------------------------------------------
| local | remote |
==============================================================================
| <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
------------------------------------------------------------------------------
{noformat}
However, in my actual query that this example is based on
(https://github.com/NatLibFi/Finto-data/blob/master/tools/yso-updater-sparql/5-ysa-removed-concepts.rq)
using FILTER NOT EXISTS is not an efficient solution, because the subtracted
part uses a federated query and it will result in almost 30000 queries to be
performed to the remote endpoint instead of just one.
I'm using the most recent snapshots available from repository.apache.org.
> sdbquery doesn't work with MINUS
> --------------------------------
>
> Key: JENA-1128
> URL: https://issues.apache.org/jira/browse/JENA-1128
> Project: Apache Jena
> Issue Type: Bug
> Components: SDB
> Affects Versions: Jena 3.0.1
> Environment: jena-sdb-3.1.0-SNAPSHOT dated 2 Feb 2016
> apache-jena-3.1.0-SNAPSHOT dated 2 Feb 2016
> Reporter: Osma Suominen
>
> I'm running a SPARQL query against a SDB loaded with SKOS data. The intent of
> the query is to check for broken links, i.e. skos:closeMatch relationships
> that point to nonexistent concepts in another SKOS dataset. I have simplified
> my query to a rather minimal test case below. In this case, also the remote
> data is included in the same graph for simplicity.
> Here is my test data:
> {noformat}
> @prefix skos: <http://www.w3.org/2004/02/skos/core#>.
> @prefix local: <http://example.com/local/>.
> @prefix remote: <http://example.com/remote/>.
> local:conceptA a skos:Concept ;
> skos:prefLabel "Local concept A"@en ;
> skos:note "has a valid link to an existing remote concept" ;
> skos:closeMatch remote:conceptC .
> local:conceptB a skos:Concept ;
> skos:prefLabel "Local concept B"@en ;
> skos:note "has a broken link to a nonexistent remote concept" ;
> skos:closeMatch remote:conceptD .
> remote:conceptC a skos:Concept ;
> skos:prefLabel "Remote concept C"@en .
> {noformat}
> This is my SPARQL query:
> {noformat}
> PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
> SELECT * WHERE {
> ?local skos:closeMatch ?remote .
> MINUS { ?remote a skos:Concept }
> }
> {noformat}
> If I run the query using the command line tool "sparql" from the apache-jena
> distribution, it returns the correct result, i.e. the one concept with the
> broken link:
> {noformat}
> ------------------------------------------------------------------------------
> | local | remote |
> ==============================================================================
> | <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
> ------------------------------------------------------------------------------
> {noformat}
> But when I load the above data into a SDB database (MySQL) and use sdbquery
> with the same SPARQL query, I get a different result (here run with the
> --debug option) which has an extra row:
> {noformat}
> PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
> SELECT *
> WHERE
> { ?local skos:closeMatch ?remote
> MINUS
> { ?remote a skos:Concept }
> }
> - - - - - - - - - - - - - -
> SELECT -- V_3=?remote
> R_3.lex AS V_3_lex, R_3.datatype AS V_3_datatype, R_3.lang AS V_3_lang,
> R_3.type AS V_3_type
> FROM
> ( SELECT -- ?remote:(T_2.s=>T_2.X_1)
> T_2.s AS X_1
> FROM Triples AS T_2 -- ?remote
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
> WHERE ( T_2.p = -6430697865200335348 -- Const:
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> AND T_2.o = 1728757386496985884 -- Const: skos:Concept
> )
> ) AS T_2 -- ?remote:(T_2.s=>T_2.X_1)
> LEFT OUTER JOIN
> Nodes AS R_3 -- Var: ?remote
> ON ( T_2.X_1 = R_3.hash )
> (minus
> (SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
> R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
> R_1.type/V_1_type
> R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
> R_2.type/V_2_type
> Join/left outer
> Join/left outer
> SqlSelectBlock/T_1
> T_1.p = 2699241716664962559
> Table T_1 -- ?local skos:closeMatch ?remote
> Table R_1 -- Var: ?local
> Condition T_1.s = R_1.hash
> Table R_2 -- Var: ?remote
> Condition T_1.o = R_2.hash''')
> (SQL '''SqlSelectBlock/S_2 -- V_3=?remote
> R_3.lex/V_3_lex R_3.datatype/V_3_datatype R_3.lang/V_3_lang
> R_3.type/V_3_type
> Join/left outer
> SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
> T_2.s/X_1
> T_2.p = -6430697865200335348
> T_2.o = 1728757386496985884
> Table T_2 -- ?remote
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
> Table R_3 -- Var: ?remote
> Condition T_2.X_1 = R_3.hash''')
> )
> SELECT -- V_1=?local V_2=?remote
> R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
> R_1.type AS V_1_type,
> R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
> R_2.type AS V_2_type
> FROM
> ( SELECT *
> FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
> WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
> )
> ) AS T_1
> LEFT OUTER JOIN
> Nodes AS R_1 -- Var: ?local
> ON ( T_1.s = R_1.hash )
> LEFT OUTER JOIN
> Nodes AS R_2 -- Var: ?remote
> ON ( T_1.o = R_2.hash )
> ------------------------------------------------------------------------------
> | local | remote |
> ==============================================================================
> | <http://example.com/local/conceptA> | <http://example.com/remote/conceptC> |
> | <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
> ------------------------------------------------------------------------------
> {noformat}
> If I change the query to use FILTER NOT EXISTS instead of MINUS, then I get
> the correct result also with sdbquery:
> {noformat}
> PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
> SELECT *
> WHERE
> { ?local skos:closeMatch ?remote
> FILTER NOT EXISTS { ?remote a skos:Concept }
> }
> - - - - - - - - - - - - - -
> (filter (notexists
> (SQL '''SqlSelectBlock/T_2 -- ?remote:(T_2.s=>T_2.X_1)
> T_2.s/X_1
> T_2.p = -6430697865200335348
> T_2.o = 1728757386496985884
> Table T_2 -- ?remote
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept''')
> )
> (SQL '''SqlSelectBlock/S_1 -- V_1=?local V_2=?remote
> R_1.lex/V_1_lex R_1.datatype/V_1_datatype R_1.lang/V_1_lang
> R_1.type/V_1_type
> R_2.lex/V_2_lex R_2.datatype/V_2_datatype R_2.lang/V_2_lang
> R_2.type/V_2_type
> Join/left outer
> Join/left outer
> SqlSelectBlock/T_1
> T_1.p = 2699241716664962559
> Table T_1 -- ?local skos:closeMatch ?remote
> Table R_1 -- Var: ?local
> Condition T_1.s = R_1.hash
> Table R_2 -- Var: ?remote
> Condition T_1.o = R_2.hash''')
> )
> SELECT -- V_1=?local V_2=?remote
> R_1.lex AS V_1_lex, R_1.datatype AS V_1_datatype, R_1.lang AS V_1_lang,
> R_1.type AS V_1_type,
> R_2.lex AS V_2_lex, R_2.datatype AS V_2_datatype, R_2.lang AS V_2_lang,
> R_2.type AS V_2_type
> FROM
> ( SELECT *
> FROM Triples AS T_1 -- ?local skos:closeMatch ?remote
> WHERE ( T_1.p = 2699241716664962559 -- Const: skos:closeMatch
> )
> ) AS T_1
> LEFT OUTER JOIN
> Nodes AS R_1 -- Var: ?local
> ON ( T_1.s = R_1.hash )
> LEFT OUTER JOIN
> Nodes AS R_2 -- Var: ?remote
> ON ( T_1.o = R_2.hash )
> SELECT *
> FROM Triples AS T_3 --
> <http://example.com/remote/conceptC>
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
> WHERE ( T_3.s = 5972767169237582230 -- Const:
> <http://example.com/remote/conceptC>
> AND T_3.p = -6430697865200335348 -- Const:
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> AND T_3.o = 1728757386496985884 -- Const: skos:Concept
> )
> SELECT *
> FROM Triples AS T_4 --
> <http://example.com/remote/conceptD>
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> skos:Concept
> WHERE ( T_4.s = 8175828786801660008 -- Const:
> <http://example.com/remote/conceptD>
> AND T_4.p = -6430697865200335348 -- Const:
> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> AND T_4.o = 1728757386496985884 -- Const: skos:Concept
> )
> ------------------------------------------------------------------------------
> | local | remote |
> ==============================================================================
> | <http://example.com/local/conceptB> | <http://example.com/remote/conceptD> |
> ------------------------------------------------------------------------------
> {noformat}
> However, in my actual query that this example is based on
> (https://github.com/NatLibFi/Finto-data/blob/master/tools/yso-updater-sparql/5-ysa-removed-concepts.rq)
> using FILTER NOT EXISTS is not an efficient solution, because the subtracted
> part uses a federated query and it will result in almost 30000 queries to be
> performed to the remote endpoint instead of just one.
> I'm using the most recent snapshots available from repository.apache.org.
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