[jira] [Created] (JENA-1815) Join strategy/VarFinder: deal with assigned variables (AS) differently to pattern defined variables.

["Andy Seaborne (Jira)" <ji...@apache.org>]

Andy Seaborne created JENA-1815:
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             Summary: Join strategy/VarFinder: deal with assigned variables (AS) differently to pattern defined variables.
                 Key: JENA-1815
                 URL: https://issues.apache.org/jira/browse/JENA-1815
             Project: Apache Jena
          Issue Type: Improvement
    Affects Versions: Jena 3.13.1, Jena 3.14.0
            Reporter: Andy Seaborne
            Assignee: Andy Seaborne


The {{VarFinder}} treats assigned variables ({{AS ?var}}) in the same way as variables set by pattern. In the sense that these two forms both set variables, this is correct but "AS variables" can not be substituted for. At the moment join classification says that a join is not "linear" (i.e. {{sequence}} can be used) when assignment is encountered.

By classifying variables into substituable and non-substitutable, it should be possible to do a better job of optimization choices of the join strategy.

This is motivated by JENA-1813.




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