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 © 2011–2016 The Apache Software Foundation. All rights reserved.