Andy Seaborne created JENA-1023:
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Summary: Join library
Key: JENA-1023
URL: https://issues.apache.org/jira/browse/JENA-1023
Project: Apache Jena
Issue Type: Improvement
Components: ARQ
Reporter: Andy Seaborne
Assignee: Andy Seaborne
This JIRA is for refactoring and adding more join algorithms into a join
library.
This is for joins between results from intermediate patterns, not joins that
solve basic graph patterns.
Normal use is a index join algorithm but it has some requirements about
variable scope. ARQ falls back to a general join mechanism if the scoping
requirements aren't met (this unusual).
The general join code is not good. It should be, for example, a hash join if
possible.
Relation to JENA-266: There is hash-based anti-join code in
{{org.apache.jena.sparql.engine.index}} in support of {{MINUS}}. This is not a
proposal to combine that code into the join library. It is not immediately
clear that code to cover all cases (inner join, left join and anti-join) at
once is really a good idea if it leads to excessively complicated code.
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