[jira] [Updated] (CASSANDRA-3638) rangeSlice may iterate the whole memtable while just query one row . This may seriously affect the performance .

["MaHaiyang (Updated) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-3638?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

MaHaiyang updated CASSANDRA-3638:
---------------------------------

    Priority: Minor  (was: Major)
     Summary: rangeSlice may iterate the whole memtable while just query one row . This may seriously affect the  performance .  (was: It may iterate the whole memtable while just query one row . This seriously affect the  performance . of Cassandra)
    
> rangeSlice may iterate the whole memtable while just query one row . This may seriously affect the  performance .
> -----------------------------------------------------------------------------------------------------------------
>
>                 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
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 3638.patch
>
>
> RangeSliceVerbHandler may  just only query one row , but cassandra may iterate the whole memtable .
> the problem is in ColumnFamilyStore.getRangeSlice() method .
> {color:red} // this iterator may iterate the whole memtable!!{color}
> {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()) // this iterator may iterate the whole memtable!!               
>                {
>                     ....
>                 }
>             }
>           .....
>         }
>        .....
>         return rows;
>     }
> {code} 
> {color:red} // Just only query one row ,but returned a sublist of columnFamiles   {color}
> {code:title=Memtable.java|borderStyle=solid}
> // Just only query one row ,but returned a sublist of columnFamiles     
> public Iterator<Map.Entry<DecoratedKey, ColumnFamily>> getEntryIterator(DecoratedKey startWith)
>     {
>         return columnFamilies.tailMap(startWith).entrySet().iterator();
>     }
> {code} 
> {color:red} // entry.getKey() will never bigger or equal to startKey, and then iterate the whole sublist of memtable {color}             
> {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);
>                 // entry.getKey() will never bigger or equal to startKey, and then iterate the whole sublist of memtable             
>                 if (pred.apply(ici))  
>                     return ici;
>             }
>             return endOfData();
> {code} 

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