org.apache.accumulo.core.iterators

Interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>

All Known Subinterfaces:

FileSKVIterator, InterruptibleIterator

All Known Implementing Classes:

AgeOffFilter, AggregatingIterator, BigDecimalCombiner, BigDecimalCombiner.BigDecimalMaxCombiner, BigDecimalCombiner.BigDecimalMinCombiner, BigDecimalCombiner.BigDecimalSummingCombiner, BloomFilterLayer.Reader, ClientSideIteratorScanner.ScannerTranslator, ColumnAgeOffFilter, ColumnFamilyCounter, ColumnFamilySkippingIterator, ColumnQualifierFilter, ColumnSliceFilter, Combiner, CountingIterator, DebugIterator, DeletingIterator, DevNull, FamilyIntersectingIterator, Filter, FirstEntryInRowIterator, GrepIterator, GrepIterator, HeapIterator, IndexedDocIterator, IntersectingIterator, IntersectingIterator, LargeRowFilter, LargeRowFilter, LongCombiner, MapFileIterator, MapFileOperations.RangeIterator, MaxCombiner, MinCombiner, MultiIterator, OrIterator, RegExFilter, ReqVisFilter, RFile.Reader, RowDeletingIterator, RowDeletingIterator, RowFilter, SequenceFileIterator, SkippingIterator, SortedKeyIterator, SortedMapIterator, SourceSwitchingIterator, StatsIterator, SummingArrayCombiner, SummingCombiner, SynchronizedIterator, TimeSettingIterator, TimestampFilter, TransformingIterator, TypedValueCombiner, VersioningIterator, VersioningIterator, VisibilityFilter, VisibilityFilter, WholeRowIterator, WholeRowIterator, WrappingIterator

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

An iterator that supports iterating over key and value pairs. Anything implementing this interface should return keys in sorted order.

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.

Method Detail

init

void init(SortedKeyValueIterator<K,V> source,
        Map<String,String> options,
        IteratorEnvironment env)
          throws IOException

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.

IllegalArgumentException - if there are problems with the options.

UnsupportedOperationException - if not supported.

hasTop

boolean hasTop()

Returns true if the iterator has more elements.

Returns:

true if the iterator has more elements.

Throws:

IllegalStateException - if called before seek.

next

void next()
          throws IOException

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.

Throws:

IOException - if an I/O error occurs.

IllegalStateException - if called before seek.

NoSuchElementException - if next element doesn't exist.

seek

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

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 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.

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.

IllegalArgumentException - if there are problems with the parameters.

getTopKey

K getTopKey()

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.

Returns:

K

Throws:

IllegalStateException - if called before seek.

NoSuchElementException - if top element doesn't exist.

getTopValue

V getTopValue()

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

Returns:

V

Throws:

IllegalStateException - if called before seek.

NoSuchElementException - if top element doesn't exist.

deepCopy

SortedKeyValueIterator<K,V> deepCopy(IteratorEnvironment env)

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.

Parameters:

env - IteratorEnvironment environment in which iterator is being run.

Returns:

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

Throws:

UnsupportedOperationException - if not supported.