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  1. Blazegraph (by SYSTAP)
  2. BLZG-8994

Query result is missing rows depending on SELECT projection

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    Details

    • Type: Bug
    • Status: Open
    • Priority: Medium
    • Resolution: Unresolved
    • Affects Version/s: BLAZEGRAPH_2_1_4
    • Fix Version/s: None
    • Component/s: Wikidata Query Service
    • Labels:
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      Description

      This query:

      SELECT ?lang ?langLabel
      WHERE {
      	{
      		SELECT ?lang ?langLabel WHERE {
      			BIND(wd:Q154755 AS ?lang)
      			SERVICE wikibase:label { bd:serviceParam wikibase:language "en" . }
      		}
      	}
      	FILTER("Ada"@en = ?langLabel) .
      }
      

      Works fine and returns one row. However, if I remove ?langLabel from projection:

      SELECT ?lang
      WHERE {
      	{
      		SELECT ?lang ?langLabel WHERE {
      			BIND(wd:Q154755 AS ?lang)
      			SERVICE wikibase:label { bd:serviceParam wikibase:language "en" . }
      		}
      	}
      	FILTER("Ada"@en = ?langLabel) .
      }
      

      It is no longer returning any rows. Removing the FILTER makes it return one row again. Looks like somehow absence of the variable in projection is taken to mean it is also absent from the query and the filter can not match?

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            Assignee:
            beebs Brad Bebee
            Reporter:
            stasmalyshev stasmalyshev
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              Dates

              Created:
              Updated: