org.apache.accumulo.core.iterators
Class FirstEntryInRowIterator

java.lang.Object
  org.apache.accumulo.core.iterators.WrappingIterator
      org.apache.accumulo.core.iterators.SkippingIterator
          org.apache.accumulo.core.iterators.FirstEntryInRowIterator

All Implemented Interfaces:

OptionDescriber, SortedKeyValueIterator<Key,Value>

public class FirstEntryInRowIterator
extends SkippingIterator
implements OptionDescriber

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.accumulo.core.iterators.OptionDescriber

OptionDescriber.IteratorOptions

Constructor Summary

FirstEntryInRowIterator()

FirstEntryInRowIterator(FirstEntryInRowIterator other, IteratorEnvironment env)

Method Summary

protected void	consume()
SortedKeyValueIterator<Key,Value>	deepCopy(IteratorEnvironment env) Creates a deep copy of this iterator as though seek had not yet been called.
OptionDescriber.IteratorOptions	describeOptions() Gets an iterator options object that contains information needed to configure this iterator.
boolean	hasTop() Returns true if the iterator has more elements.
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.
static void	setNumScansBeforeSeek(IteratorSetting cfg, int num) convenience method to set the option to optimize the frequency of scans vs.
static void	setNumScansBeforeSeek(Scanner scanner, String iteratorName, int num) Deprecated. since 1.4, use setNumScansBeforeSeek(IteratorSetting, int)
boolean	validateOptions(Map<String,String> options) Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.

Methods inherited from class org.apache.accumulo.core.iterators.SkippingIterator

next

Methods inherited from class org.apache.accumulo.core.iterators.WrappingIterator

getSource, getTopKey, getTopValue, setSource

Methods inherited from class java.lang.Object

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

Constructor Detail

FirstEntryInRowIterator

public FirstEntryInRowIterator()

FirstEntryInRowIterator

public FirstEntryInRowIterator(FirstEntryInRowIterator other,
                               IteratorEnvironment env)

Method Detail

setNumScansBeforeSeek

public static void setNumScansBeforeSeek(Scanner scanner,
                                         String iteratorName,
                                         int num)

Deprecated. since 1.4, use setNumScansBeforeSeek(IteratorSetting, int)

Parameters:

scanner -

iteratorName -

num -

setNumScansBeforeSeek

public static void setNumScansBeforeSeek(IteratorSetting cfg,
                                         int num)

convenience method to set the option to optimize the frequency of scans vs. seeks

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>

Overrides:

deepCopy in class WrappingIterator

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

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

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.

Specified by:

init in interface SortedKeyValueIterator<Key,Value>

Overrides:

init in class WrappingIterator

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.

consume

protected void consume()
                throws IOException

Specified by:

consume in class SkippingIterator

Throws:

IOException

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>

Overrides:

hasTop in class WrappingIterator

Returns:

true if the iterator has more elements.

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, irregardless 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<Key,Value>

Overrides:

seek in class SkippingIterator

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.

describeOptions

public OptionDescriber.IteratorOptions describeOptions()

Description copied from interface: OptionDescriber

Gets an iterator options object that contains information needed to configure this iterator. This object will be used by the accumulo shell to prompt the user to input the appropriate information.

Specified by:

describeOptions in interface OptionDescriber

Returns:

an iterator options object

validateOptions

public boolean validateOptions(Map<String,String> options)

Description copied from interface: OptionDescriber

Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.

Specified by:

validateOptions in interface OptionDescriber

Parameters:

options - a map of option names to option values

Returns:

true if options are valid, false otherwise