org.apache.accumulo.core.iterators
public class FirstEntryInRowIterator extends SkippingIterator implements OptionDescriber
OptionDescriber.IteratorOptions
Constructor and Description |
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FirstEntryInRowIterator() |
FirstEntryInRowIterator(FirstEntryInRowIterator other,
IteratorEnvironment env) |
Modifier and Type | Method and Description |
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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.
|
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.
|
next
getSource, getTopKey, getTopValue, setSource
public FirstEntryInRowIterator()
public FirstEntryInRowIterator(FirstEntryInRowIterator other, IteratorEnvironment env)
public static void setNumScansBeforeSeek(IteratorSetting cfg, int num)
public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
SortedKeyValueIterator
deepCopy
in interface SortedKeyValueIterator<Key,Value>
deepCopy
in class WrappingIterator
env
- IteratorEnvironment environment in which iterator is being run.public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env) throws IOException
SortedKeyValueIterator
init
in interface SortedKeyValueIterator<Key,Value>
init
in class WrappingIterator
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.protected void consume() throws IOException
consume
in class SkippingIterator
IOException
public boolean hasTop()
SortedKeyValueIterator
hasTop
in interface SortedKeyValueIterator<Key,Value>
hasTop
in class WrappingIterator
public void seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive) throws IOException
SortedKeyValueIterator
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, 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.seek
in interface SortedKeyValueIterator<Key,Value>
seek
in class SkippingIterator
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.public OptionDescriber.IteratorOptions describeOptions()
OptionDescriber
describeOptions
in interface OptionDescriber
public boolean validateOptions(Map<String,String> options)
OptionDescriber
validateOptions
in interface OptionDescriber
options
- a map of option names to option valuesCopyright © 2014 Apache Accumulo Project. All Rights Reserved.