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java.lang.Objectorg.apache.accumulo.core.iterators.user.RowDeletingIterator
public class RowDeletingIterator
An iterator for deleting whole rows. After setting this iterator up for your table, to delete a row insert a row with empty column family, empty column qualifier, empty column visibility, and a value of DEL_ROW. Do not use empty columns for anything else when using this iterator. When using this iterator the locality group containing the row deletes will always be read. The locality group containing the empty column family will contain row deletes. Always reading this locality group can have an impact on performance. For example assume there are two locality groups, one containing large images and one containing small metadata about the images. If row deletes are in the same locality group as the images, then this will significantly slow down scans and major compactions that are only reading the metadata locality group. Therefore, you would want to put the empty column family in the locality group that contains the metadata. Another option is to put the empty column in its own locality group. Which is best depends on your data.
Field Summary | |
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static Value |
DELETE_ROW_VALUE
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Constructor Summary | |
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RowDeletingIterator()
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Method Summary | |
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SortedKeyValueIterator<Key,Value> |
deepCopy(IteratorEnvironment env)
Creates a deep copy of this iterator as though seek had not yet been called. |
Key |
getTopKey()
Returns top key. |
Value |
getTopValue()
Returns top value. |
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 |
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. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final Value DELETE_ROW_VALUE
Constructor Detail |
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public RowDeletingIterator()
Method Detail |
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public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
SortedKeyValueIterator
deepCopy
in interface SortedKeyValueIterator<Key,Value>
env
- IteratorEnvironment environment in which iterator is being run.
public Key getTopKey()
SortedKeyValueIterator
getTopKey
in interface SortedKeyValueIterator<Key,Value>
public Value getTopValue()
SortedKeyValueIterator
getTopValue
in interface SortedKeyValueIterator<Key,Value>
public boolean hasTop()
SortedKeyValueIterator
hasTop
in interface SortedKeyValueIterator<Key,Value>
public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env) throws IOException
SortedKeyValueIterator
init
in interface SortedKeyValueIterator<Key,Value>
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.public void next() throws IOException
SortedKeyValueIterator
next
in interface SortedKeyValueIterator<Key,Value>
IOException
- if an I/O error occurs.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, 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.
seek
in interface SortedKeyValueIterator<Key,Value>
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.
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