org.apache.accumulo.core.iterators.system

Class SynchronizedIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

java.lang.Object

org.apache.accumulo.core.iterators.system.SynchronizedIterator<K,V>

All Implemented Interfaces:

SortedKeyValueIterator<K,V>

public class SynchronizedIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>
extends Object
implements SortedKeyValueIterator<K,V>

SynchronizedIterator: wrap a SortedKeyValueIterator so that all of its methods are synchronized

Constructor Summary

Constructors

Constructor and Description
SynchronizedIterator()
SynchronizedIterator(SortedKeyValueIterator<K,V> source)

Method Summary

Methods

Modifier and Type	Method and Description
SortedKeyValueIterator<K,V>	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
K	getTopKey() Returns top key.
V	getTopValue() Returns top value.
boolean	hasTop() Returns true if the iterator has more elements.
void	init(SortedKeyValueIterator<K,V> source, Map<String,String> options, IteratorEnvironment env) Initializes the iterator.
void	next() Advances to the next K,V pair.
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 java.lang.Object

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

Constructor Detail

SynchronizedIterator

public SynchronizedIterator()

SynchronizedIterator

public SynchronizedIterator(SortedKeyValueIterator<K,V> source)

Method Detail

init

public void init(SortedKeyValueIterator<K,V> 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.

Specified by:

init in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

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.

hasTop

public boolean hasTop()

Description copied from interface: SortedKeyValueIterator

Returns true if the iterator has more elements.

Specified by:

hasTop in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

Returns:

true if the iterator has more elements.

next

public void next()
          throws IOException

Description copied from interface: SortedKeyValueIterator

Advances to the next K,V pair. Note that in minor compaction scope and in non-full major compaction scopes the iterator may see deletion entries. These entries should be preserved by all iterators except ones that are strictly scan-time iterators that will never be configured for the minc or majc scopes. Deletion entries are only removed during full major compactions.

Specified by:

next in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

Throws:

IOException - if an I/O error occurs.

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, java.util.Map, 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.

Specified by:

seek in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

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.

getTopKey

public K getTopKey()

Description copied from interface: SortedKeyValueIterator

Returns top key. Can be called 0 or more times without affecting behavior of next() or hasTop(). Note that in minor compaction scope and in non-full major compaction scopes the iterator may see deletion entries. These entries should be preserved by all iterators except ones that are strictly scan-time iterators that will never be configured for the minc or majc scopes. Deletion entries are only removed during full major compactions.

Specified by:

getTopKey in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

Returns:

K

getTopValue

public V getTopValue()

Description copied from interface: SortedKeyValueIterator

Returns top value. Can be called 0 or more times without affecting behavior of next() or hasTop().

Specified by:

getTopValue in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

Returns:

V

deepCopy

public SortedKeyValueIterator<K,V> 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.

Specified by:

deepCopy in interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

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