GraphDB does not optimize away un-selected OPTIONAL clauses

[kevinstadler]

DISTINCT and COUNT queries like

PREFIX crm: <http://www.cidoc-crm.org/cidoc-crm/>
PREFIX lrmoo: <http://iflastandards.info/ns/lrm/lrmoo/>
PREFIX star: <https://r11.eu/ns/star/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX r11: <https://r11.eu/ns/spec/>
PREFIX r11pros: <https://r11.eu/ns/prosopography/>

select (count(distinct ?person) as ?cnt)

WHERE {
?person a crm:E21_Person.
  OPTIONAL {  ?person__person_id_assignment a crm:E15_Identifier_Assignment.  ?person ^crm:P140_assigned_attribute_to ?person__person_id_assignment.  }
  OPTIONAL {  ?person__person_appellation_assertion a star:E13_crm_P1.  ?person ^crm:P140_assigned_attribute_to ?person__person_appellation_assertion.      ?person__person_appellation_assertion crm:P141_assigned ?person__person_appellation_assertion___pai.    ?person__person_appellation_assertion___pai crm:P190_has_symbolic_content ?person__person_appellation_assertion__person_appellation_is.  }
  OPTIONAL {  ?person__person_gender_assertion a star:E13_crm_P41.  ?person ^crm:P141_assigned ?person__person_gender_assertion.  }
  OPTIONAL {  ?person__person_ethnicity_assertion a star:E13_crm_P107.  ?person ^crm:P141_assigned ?person__person_ethnicity_assertion.  }
  OPTIONAL {  ?person crm:P3_has_note ?person__person_descriptive_name.  }
  OPTIONAL {  ?person__person_possession_assertion a star:E13_crm_P51.  ?person ^crm:P141_assigned ?person__person_possession_assertion.  }
  OPTIONAL {  ?person__person_status_assertion a star:E13_sdhss_P26.  ?person ^crm:P141_assigned ?person__person_status_assertion.  }
  OPTIONAL {  ?person__person_religion_assertion a star:E13_sdhss_P36.  ?person ^crm:P141_assigned ?person__person_religion_assertion.  }
  OPTIONAL {  ?person__person_occupation_assertion a star:E13_sdhss_P13.  ?person ^crm:P141_assigned ?person__person_occupation_assertion.  }
  OPTIONAL {  ?person__person_language_assertion a star:E13_sdhss_P38.  ?person ^crm:P140_assigned_attribute_to ?person__person_language_assertion.  }
  OPTIONAL {  ?person__person_kinship_assertion a star:E13_sdhss_P17.  ?person ^crm:P141_assigned ?person__person_kinship_assertion.  }
}

take ages to execute, even though the simple query

 PREFIX crm: <http://www.cidoc-crm.org/cidoc-crm/>
PREFIX lrmoo: <http://iflastandards.info/ns/lrm/lrmoo/>
PREFIX star: <https://r11.eu/ns/star/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX r11: <https://r11.eu/ns/spec/>
PREFIX r11pros: <https://r11.eu/ns/prosopography/>

select (count(distinct ?person) as ?cnt)

WHERE {
?person a crm:E21_Person.
}

would yield the same result.

Suggested fix: rdfproxy should strip OPTIONAL clauses during query injection.

[lu-pl]

Removed bug label. This is not an RDFProxy bug.