[jira] [Comment Edited] (JENA-1023) Algebra execution join library

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

    [ https://issues.apache.org/jira/browse/JENA-1023?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14742542#comment-14742542 ] 

Andy Seaborne edited comment on JENA-1023 at 9/13/15 4:51 PM:
--------------------------------------------------------------

Commit 05c9eae484650bfaa585f41ac77284bb0c38b17f in jena's branch refs/heads/master from [~andy.seaborne]
[ https://git-wip-us.apache.org/repos/asf?p=jena.git;h=05c9eae ]

JENA-1023: Letf join support.

Refactor for common hasgh-join engine in AbstractIterHashJoin.
Different implementations.
2 version for LeftJoin, depending on which side is used to build the
hash table.



was (Author: jira-bot):
Commit 05c9eae484650bfaa585f41ac77284bb0c38b17f in jena's branch refs/heads/master from [~andy.seaborne]
[ https://git-wip-us.apache.org/repos/asf?p=jena.git;h=05c9eae ]

JENA-1023: Letf join support.

Refactor for common hasgh-join engine in AbstractIterHashJoin.
Different implements.
2 version for LeftJoin, depending on which side is used to build the
hash table.


> Algebra execution 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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