org.apache.accumulo.core.iterators.system

Class MultiIterator

java.lang.Object

org.apache.accumulo.core.iterators.system.HeapIterator

org.apache.accumulo.core.iterators.system.MultiIterator

All Implemented Interfaces:

SortedKeyValueIterator<Key,Value>, YieldingKeyValueIterator<Key,Value>

public class MultiIterator
extends HeapIterator

An iterator capable of iterating over other iterators in sorted order.

Constructor Summary

Constructors

Constructor and Description
MultiIterator(List<SortedKeyValueIterator<Key,Value>> readers, boolean init)
MultiIterator(List<SortedKeyValueIterator<Key,Value>> iters2, KeyExtent extent)
MultiIterator(List<SortedKeyValueIterator<Key,Value>> iters, Range seekFence)

Method Summary

Modifier and Type	Method and Description
MultiIterator	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
void	init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env) Initializes the iterator.
void	seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive) Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns.

Methods inherited from class org.apache.accumulo.core.iterators.system.HeapIterator

addSource, clear, createHeap, getTopKey, getTopValue, hasTop, next

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator

enableYielding

Constructor Detail

MultiIterator

public MultiIterator(List<SortedKeyValueIterator<Key,Value>> iters,
                     Range seekFence)

MultiIterator

public MultiIterator(List<SortedKeyValueIterator<Key,Value>> iters2,
                     KeyExtent extent)

MultiIterator

public MultiIterator(List<SortedKeyValueIterator<Key,Value>> readers,
                     boolean init)

Method Detail

deepCopy

public MultiIterator deepCopy(IteratorEnvironment env)

Description copied from interface: SortedKeyValueIterator

Creates a deep copy of this iterator as though seek had not yet been called. init should be called on an iterator before deepCopy is called. init should not need to be called on the copy that is returned by deepCopy; that is, when necessary init should be called in the deepCopy method on the iterator it returns. The behavior is unspecified if init is called after deepCopy either on the original or the copy. A proper implementation would call deepCopy on the source.

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

SortedKeyValueIterator a copy of this iterator (with the same source and settings).

seek

public void seek(Range range,
                 Collection<ByteSequence> columnFamilies,
                 boolean inclusive)
          throws IOException

Description copied from interface: SortedKeyValueIterator

Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns. An iterator does not have to stop at the end of the range. The whole range is provided so that iterators can make optimizations. Seek may be called multiple times with different parameters after SortedKeyValueIterator.init(org.apache.accumulo.core.iterators.SortedKeyValueIterator<K, V>, java.util.Map<java.lang.String, java.lang.String>, org.apache.accumulo.core.iterators.IteratorEnvironment) is called. Iterators that examine groups of adjacent key/value pairs (e.g. rows) to determine their top key and value should be sure that they properly handle a seek to a key in the middle of such a group (e.g. the middle of a row). Even if the client always seeks to a range containing an entire group (a,c), the tablet server could send back a batch of entries corresponding to (a,b], then reseek the iterator to range (b,c) when the scan is continued. columnFamilies is used, at the lowest level, to determine which data blocks inside of an RFile need to be opened for this iterator. This set of data blocks is also the set of locality groups defined for the given table. If no columnFamilies are provided, the data blocks for all locality groups inside of the correct RFile will be opened and seeked in an attempt to find the correct start key, regardless of the startKey in the range. In an Accumulo instance in which multiple locality groups exist for a table, it is important to ensure that columnFamilies is properly set to the minimum required column families to ensure that data from separate locality groups is not inadvertently read.

Parameters:

range - Range of keys to iterate over.

columnFamilies - Collection of column families to include or exclude.

inclusive - boolean that indicates whether to include (true) or exclude (false) column families.

Throws:

IOException - if an I/O error occurs.

init

public void init(SortedKeyValueIterator<Key,Value> source,
                 Map<String,String> options,
                 IteratorEnvironment env)
          throws IOException

Description copied from interface: SortedKeyValueIterator

Initializes the iterator. Data should not be read from the source in this method.

Parameters:

source - SortedKeyValueIterator source to read data from.

options - Map map of string option names to option values.

env - IteratorEnvironment environment in which iterator is being run.

Throws:

IOException - unused.