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https://issues.apache.org/jira/browse/CASSANDRA-12796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15731712#comment-15731712
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Milan Majercik commented on CASSANDRA-12796:
--------------------------------------------
Excellent. This is the closest we can get to keep target page size in bytes. Do
you want me to test it with our test data? If not, could it be merged into the
primary repository?
> Heap exhaustion when rebuilding secondary index over a table with wide
> partitions
> ---------------------------------------------------------------------------------
>
> Key: CASSANDRA-12796
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12796
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Milan Majercik
> Priority: Critical
>
> We have a table with rather wide partition and a secondary index defined over
> it. As soon as we try to rebuild the index we observed exhaustion of Java
> heap and eventual OOM error. After a lengthy investigation we have managed to
> find a culprit which appears to be a wrong granule of barrier issuances in
> method {{org.apache.cassandra.db.Keyspace.indexRow}}:
> {code}
> try (OpOrder.Group opGroup = cfs.keyspace.writeOrder.start()){html}
> {
> Set<SecondaryIndex> indexes =
> cfs.indexManager.getIndexesByNames(idxNames);
> Iterator<ColumnFamily> pager = QueryPagers.pageRowLocally(cfs,
> key.getKey(), DEFAULT_PAGE_SIZE);
> while (pager.hasNext())
> {
> ColumnFamily cf = pager.next();
> ColumnFamily cf2 = cf.cloneMeShallow();
> for (Cell cell : cf)
> {
> if (cfs.indexManager.indexes(cell.name(), indexes))
> cf2.addColumn(cell);
> }
> cfs.indexManager.indexRow(key.getKey(), cf2, opGroup);
> }
> }
> {code}
> Please note the operation group granule is a partition of the source table
> which poses a problem for wide partition tables as flush runnable
> ({{org.apache.cassandra.db.ColumnFamilyStore.Flush.run()}}) won't proceed
> with flushing secondary index memtable before completing operations prior
> recent issue of the barrier. In our situation the flush runnable waits until
> whole wide partition gets indexed into the secondary index memtable before
> flushing it. This causes an exhaustion of the heap and eventual OOM error.
> After we changed granule of barrier issue in method
> {{org.apache.cassandra.db.Keyspace.indexRow}} to query page as opposed to
> table partition secondary index (see
> [https://github.com/mmajercik/cassandra/commit/7e10e5aa97f1de483c2a5faf867315ecbf65f3d6?diff=unified]),
> rebuild started to work without heap exhaustion.
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