public interface SortedKeyValueIterator<K extends org.apache.hadoop.io.WritableComparable<?>,V extends org.apache.hadoop.io.Writable>
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.
|
void init(SortedKeyValueIterator<K,V> source, Map<String,String> options, IteratorEnvironment env) throws IOException
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.IOException
- unused.IllegalArgumentException
- if there are problems with the options.UnsupportedOperationException
- if not supported.boolean hasTop()
IllegalStateException
- if called before seek.void next() throws IOException
IOException
- if an I/O error occurs.IllegalStateException
- if called before seek.NoSuchElementException
- if next element doesn't exist.void seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive) throws IOException
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.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.IOException
- if an I/O error occurs.IllegalArgumentException
- if there are problems with the parameters.K getTopKey()
For performance reasons, iterators reserve the right to reuse objects returned by
getTopKey when next()
is called, changing the data that the object
references. Iterators that need to save an object returned by getTopKey ought to copy
the object's data into a new object in order to avoid aliasing bugs.
IllegalStateException
- if called before seek.NoSuchElementException
- if top element doesn't exist.V getTopValue()
For performance reasons, iterators reserve the right to reuse objects returned by
getTopValue when next()
is called, changing the underlying data that the
object references. Iterators that need to save an object returned by getTopValue ought
to copy the object's data into a new object in order to avoid aliasing bugs.
IllegalStateException
- if called before seek.NoSuchElementException
- if top element doesn't exist.SortedKeyValueIterator<K,V> deepCopy(IteratorEnvironment env)
env
- IteratorEnvironment environment in which iterator is being run.UnsupportedOperationException
- if not supported.Copyright © 2011–2018 The Apache Software Foundation. All rights reserved.