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https://issues.apache.org/jira/browse/MARMOTTA-175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617296#comment-13617296
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Raffaele Palmieri commented on MARMOTTA-175:
--------------------------------------------
Hi Sebastian, left join/is null is an optimized construct on the major part of
RDBMS, anyway there is a third possibility with NOT IN clause with this command:
---------------------------------
delete FROM triples WHERE
triples.deleted = true
AND
triples.id not in (SELECT triple_id FROM reasoner_just_supp_triples)
AND
triples.id not in (SELECT triple_id FROM versions_added)
AND
triples.id not in (SELECT triple_id FROM versions_removed)
-----------------------------------
>From some test that I've done on 15K triples, NOT IN is the most efficient
>query,
following time results in ms
not in=3
left join=14
not exists=24
> Garbage collection on triple tables
> -----------------------------------
>
> Key: MARMOTTA-175
> URL: https://issues.apache.org/jira/browse/MARMOTTA-175
> Project: Marmotta
> Issue Type: Bug
> Components: Triple Store
> Affects Versions: 3.1-incubating
> Environment: Centos 6.4 64b - JDK 1.6.0_38 - MySql 5.1.67 - Tomcat
> 7.0.37
> Reporter: Raffaele Palmieri
> Assignee: Sebastian Schaffert
> Priority: Minor
> Labels: garbage, mysql, triplestore
>
> During garbage collection of triple tables in log there is the following line:
> SQL error while executing garbage collection on triples table: You have an
> error in your SQL syntax; check the manual that corresponds to your MySQL
> server version for the right syntax to use near 'UNION (SELECT triple_id FROM
> reasoner_just_supp_triples WHERE triple_id = triple' at line 1
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