org.apache.accumulo.core.iterators
Class WholeRowIterator

java.lang.Object
  org.apache.accumulo.core.iterators.WholeRowIterator

All Implemented Interfaces:

SortedKeyValueIterator<Key,Value>

public class WholeRowIterator
extends java.lang.Object
implements SortedKeyValueIterator<Key,Value>

The WholeRowIterator is designed to provide row-isolation so that queries see mutations as atomic. It does so by encapsulating an entire row of key/value pairs into a single key/value pair, which is returned through the client as an atomic operation.

One caveat is that when seeking in the WholeRowIterator using a range that starts at a non-inclusive first key in a row, (e.g. seek(new Range(new Key(new Text("row")),false,...),...)) this iterator will skip to the next row. This is done in order to prevent repeated scanning of the same row when system automatically creates ranges of that form, which happens in the case of the client calling continueScan, or in the case of the tablet server continuing a scan after swapping out sources.

To regain the original key/value pairs of the row, call the decodeRow function on the key/value pair that this iterator returned.

Constructor Summary

WholeRowIterator()

Method Summary

static java.util.SortedMap<Key,Value>	decodeRow(Key rowKey, Value rowValue)
SortedKeyValueIterator<Key,Value>	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
static Value	encodeRow(java.util.List<Key> keys, java.util.List<Value> values)
protected boolean	filter(org.apache.hadoop.io.Text currentRow, java.util.List<Key> keys, java.util.List<Value> values)
Key	getTopKey() Returns top key.
Value	getTopValue() Returns top value.
boolean	hasTop() Returns true if the iterator has more elements.
void	init(SortedKeyValueIterator<Key,Value> source, java.util.Map<java.lang.String,java.lang.String> options, IteratorEnvironment env) Initializes the iterator.
void	next() Advances to the next K,V pair.
void	seek(Range range, java.util.Collection<ByteSequence> columnFamilies, boolean inclusive) An iterator must seek to the first key in the range taking inclusiveness into account.

Methods inherited from class java.lang.Object

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

Constructor Detail

WholeRowIterator

public WholeRowIterator()

Method Detail

decodeRow

public static final java.util.SortedMap<Key,Value> decodeRow(Key rowKey,
                                                             Value rowValue)
                                                      throws java.io.IOException

Throws:

java.io.IOException

encodeRow

public static final Value encodeRow(java.util.List<Key> keys,
                                    java.util.List<Value> values)
                             throws java.io.IOException

Throws:

java.io.IOException

filter

protected boolean filter(org.apache.hadoop.io.Text currentRow,
                         java.util.List<Key> keys,
                         java.util.List<Value> values)

Parameters:

currentRow - All keys have this in their row portion (do not modify!).

keys - One key for each key in the row, ordered as they are given by the source iterator (do not modify!).

values - One value for each key in keys, ordered to correspond to the ordering in keys (do not modify!).

Returns:

true if we want to keep the row, false if we want to skip it

deepCopy

public SortedKeyValueIterator<Key,Value> 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<Key,Value>

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

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

getTopKey

public Key getTopKey()

Description copied from interface: SortedKeyValueIterator

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

Specified by:

getTopKey in interface SortedKeyValueIterator<Key,Value>

Returns:

K

getTopValue

public Value 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<Key,Value>

Returns:

V

hasTop

public boolean hasTop()

Description copied from interface: SortedKeyValueIterator

Returns true if the iterator has more elements.

Specified by:

hasTop in interface SortedKeyValueIterator<Key,Value>

Returns:

true if the iterator has more elements.

init

public void init(SortedKeyValueIterator<Key,Value> source,
                 java.util.Map<java.lang.String,java.lang.String> options,
                 IteratorEnvironment env)
          throws java.io.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<Key,Value>

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:

java.io.IOException - unused.

next

public void next()
          throws java.io.IOException

Description copied from interface: SortedKeyValueIterator

Advances to the next K,V pair.

Specified by:

next in interface SortedKeyValueIterator<Key,Value>

Throws:

java.io.IOException - if an I/O error occurs.

seek

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

Description copied from interface: SortedKeyValueIterator

An iterator must seek to the first key in the range taking inclusiveness into account. However, an iterator does not have to stop at the end of the range. The whole range is provided so that iterators can make optimizations.

Specified by:

seek in interface SortedKeyValueIterator<Key,Value>

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:

java.io.IOException - if an I/O error occurs.