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https://issues.apache.org/jira/browse/JENA-804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14182530#comment-14182530
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Osma Suominen commented on JENA-804:
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Here are my own similar findings. I've noticed the same behavior with TDB sizes
growing over time but assumed it was expected, as there are many discussions
ending with the suggestion "just dump into n-triples and reload once in a
while".
I created a test script (will attach) which starts up Fuseki (1.1.1) using the
stock config-tdb.ttl configuration and PUTs the same RDF file 20 times, while
measuring the TDB size. I used the NYTimes People dataset
(http://data.nytimes.com/people.rdf) for this test. It has about 100k triples
and no blank nodes.
I will attach the full script output, but it's quite obvious that the TDB size
is ballooning:
{noformat}
Round 1
19M DB2
Round 2
31M DB2
Round 3
42M DB2
...
Round 10
123M DB2
...
Round 20
239M DB2
{noformat}
> Jena is not reusing already allocated space on the file system which results
> in large amounts of disk space reserved by Jena files
> ----------------------------------------------------------------------------------------------------------------------------------
>
> Key: JENA-804
> URL: https://issues.apache.org/jira/browse/JENA-804
> Project: Apache Jena
> Issue Type: Bug
> Components: Jena
> Affects Versions: Jena 2.11.2, TDB 1.0.2
> Environment: Windows 7, IBM JRE 1.7, Tomcat 7.0.54
> Reporter: Keith Wells
>
> We have a product based on Jena TDB where we insert quads to Jena TDB along
> with the deletion of quads. We understand the performance over space
> architectural decision to not clean up deleted nodeids from the indexes. But
> the usage of disk space appears that Jena TDB is not reusing allocated space
> which had been allocated by Jena previously. Based on this comment there
> appears to be something that is not correct on file space utilization,
> http://mail-archives.apache.org/mod_mbox/jena-users/201310.mbox/%3cce7d7929.2a707%[email protected]%3E:
> "The indexes won't shrink - TDB never gives disk space back to the OS - but
> disk space is reused when reallocated within the same JVM.".
> In this scenario on the same JVM with NO server stops or starts, we add 27765
> graphs to IndexTdb and immediately remove them, repeating this process
> several times.
> {noformat}
> MB Bytes Diff (Bytes)
> Start 193 203239424
>
> Reindex 5 249 262066176 58826752
> Reindex 6 249 262086656 20480
> Reindex 10 298 312500224 50413568
> Reindex 11 298 312520704 20480
> Reindex 12 298 312541184 20480
> Reindex 13 298 312586240 45056
> Reindex 14 306 320995328 8409088
> Reindex 15 330 346181632 25186304
> Reindex 16 330 346198538 16906
> Reindex 17 346 362999808 16801270
> Reindex 18 346 363020288 20480
> Reindex 19 346 363040768 20480
> Reindex 20 346 363061248 20480
> Reindex 21 346 363081728 20480
> Reindex 22 354 371490816 8409088
> Reindex 23 378 396677120 25186304
>
> End 193 203239424
> {noformat}
> The system starts with 193MB of data allocated by indexTdb. A reindex
> consists of a remove followed by an add of these graphs. As you can see from
> the data there is a dramatic increase in the size of indexTdb on the disk
> after repeadedly removing and adding graphs. After Reindex 23, there is 378
> MB of disk space used. If Jena TDB reused allocated space there would be no
> need to allocate more space other than what is used by deleted node ids
> (unless nodeid storage is eating all of this space?). Jena does not appear
> to be reusing the allocated disk space. At the very end of this scenario, we
> exported the nquads and reloaded them to show the original disk space was
> 193MB back to where it started.
> We believe Jena TDB is not reusing the space allocated by the TDB file system
> within the same JVM.
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