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