It may iterate the whole memtable while just query one row . This seriously
affect the performance . of Cassandra
------------------------------------------------------------------------------------------------------------------
Key: CASSANDRA-3638
URL: https://issues.apache.org/jira/browse/CASSANDRA-3638
Project: Cassandra
Issue Type: Bug
Components: Core
Affects Versions: 1.0.0
Reporter: MaHaiyang
RangeSliceVerbHandler may just only query one row , but cassandra may iterate
the whole memtable .
the problem is in ColumnFamilyStore.getRangeSlice() method .
{code:title=ColumnFamilyStore.java|borderStyle=solid}
public List<Row> getRangeSlice(ByteBuffer superColumn, final AbstractBounds
range, int maxResults, IFilter columnFilter)
throws ExecutionException, InterruptedException
{
...
DecoratedKey startWith = new DecoratedKey(range.left, null);
DecoratedKey stopAt = new DecoratedKey(range.right, null);
QueryFilter filter = new QueryFilter(null, new QueryPath(columnFamily,
superColumn, null), columnFilter);
int gcBefore = (int)(System.currentTimeMillis() / 1000) -
metadata.getGcGraceSeconds();
List<Row> rows;
ViewFragment view = markReferenced(startWith, stopAt);
try
{
CloseableIterator<Row> iterator =
RowIteratorFactory.getIterator(view.memtables, view.sstables, startWith,
stopAt, filter, getComparator(), this);
rows = new ArrayList<Row>();
try
{
// pull rows out of the iterator
boolean first = true;
while (iterator.hasNext()) {color:red}
// this iterator may iterate the whole memtable!!
{color}
{
....
}
}
.....
}
.....
return rows;
}
{code}
{code:title=Memtable.java|borderStyle=solid}
{color:red}
// Just only query one row ,but returned a sublist of columnFamiles
{color}
public Iterator<Map.Entry<DecoratedKey, ColumnFamily>>
getEntryIterator(DecoratedKey startWith)
{
return columnFamilies.tailMap(startWith).entrySet().iterator();
}
{code}
{code:title=RowIteratorFactory.java|borderStyle=solid}
public IColumnIterator computeNext()
{
while (iter.hasNext())
{
Map.Entry<DecoratedKey, ColumnFamily> entry = iter.next();
IColumnIterator ici =
filter.getMemtableColumnIterator(entry.getValue(), entry.getKey(), comparator);
{color:red}
// entry.getKey() will never bigger or equal to startKey, and then iterate the
whole sublist of memtable
{color}
if (pred.apply(ici))
return ici;
}
return endOfData();
{code}
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
