ScanAllRangesCommandIterator (apache-cassandra API)

java.lang.Object
- org.apache.cassandra.utils.AbstractIterator<RowIterator>
- - org.apache.cassandra.service.reads.range.RangeCommandIterator
  - - org.apache.cassandra.service.reads.range.ScanAllRangesCommandIterator

All Implemented Interfaces:

com.google.common.collect.PeekingIterator<RowIterator>, java.lang.AutoCloseable, java.util.Iterator<RowIterator>, BasePartitionIterator<RowIterator>, PartitionIterator, CloseableIterator<RowIterator>
```
public class ScanAllRangesCommandIterator
extends RangeCommandIterator
```
A custom RangeCommandIterator that queries all replicas required by consistency level at once with data range specify in PartitionRangeReadCommand.
This is to speed up Index.QueryPlan.isTopK() queries that needs to find global top-k rows in the cluster, because existing RangeCommandIterator has to execute a top-k search per vnode range which is wasting resources.
The implementation combines the replica plans for each data range into a single shared replica plan. This results in queries using reconciliation where it may not be expected. This is handled in the DataResolver for top-K queries so any usage for queries other that top-K should bear this in mind.
It is important to note that this implementation can only be used with ConsistencyLevel.ONE and ConsistencyLevel.LOCAL_ONE

- Field Summary
  - Fields inherited from class org.apache.cassandra.service.reads.range.RangeCommandIterator
    rangeMetrics
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  protected PartitionIterator sendNextRequests()
  - Methods inherited from class org.apache.cassandra.service.reads.range.RangeCommandIterator
    close, computeNext
  - Methods inherited from class org.apache.cassandra.utils.AbstractIterator
    endOfData, hasNext, next, peek, remove
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  - Methods inherited from interface java.util.Iterator
    forEachRemaining, hasNext

Method Detail

sendNextRequests

protected PartitionIterator sendNextRequests()