Batch import times increase drastically as repository size increases; patch to
mitigate the problem
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Key: DS-470
URL: http://jira.dspace.org/jira/browse/DS-470
Project: DSpace 1.x
Issue Type: Improvement
Components: DSpace API
Affects Versions: 1.6.0
Reporter: Simon Brown
Priority: Minor
Attachments: batch_importer_speedup.patch
As mentioned by my colleague Tom De Mulder on dspace-tech and at
http://tdm27.wordpress.com/2010/01/19/dspace-1-6-scalability-testing/
As the repository grows, the time taken for batch imports to run also
increases. Having profiled the importer in our 1.6.0-RC1 install we determined
that most (80%-90%) of the time was spent in calls to
IndexBrowse.pruneIndexes().
The reason for this is that IndexBrowse.indexItem() calls pruneIndexes(), so
every time an item is indexed, the indexes are pruned. For any batch of size n,
where n > 1, this is (n - 1) times more than is necessary.
Increasing the visibility of pruneIndexes(), removing the call from
IndexBrowse.indexItem(), and making a single call at the end of the
BrowseConsumer.end() method reduces this to once per event queue run.
However, the batch importer calls Context.commit() after each item is imported.
Context.commit() runs the event queue, thus causing one event queue run per
imported item.
This patch addresses both of these issues in a way which has a minimal effect
on the rest of the code base; I don't necessarily consider it to be the "best"
way, but I wanted to keep the patch small so it could be put out. What it does
is:
1. create an IndexBrowse.indexItemNoPrune() method, which is called from the
BrowseConsumer class instead of indexItem(). Other calls to indexItem() are not
affected.
2. Call pruneIndexes() from BrowseConsumer.end()
3. Change the call in the batch importer from Context.commit() to
Context.getDBConnection.commit(). The only effective difference between the two
is that the event queue is not run; I think that a better solution might be to
move the code to run the event queue from the Context.commit() method to the
Context.complete() method, but I don't know what effect that will have on the
rest of the code.
As noted in Tom's blog post linked above, these changes, on a repository with
in excess of 120,000 items, brought import time from 4.7 seconds/item down to
4.9 items/second.
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