public class OrIterator extends Object implements SortedKeyValueIterator<Key,Value>, OptionDescriber
SortedKeyValueIterator
. It returns Keys in row+colqual
order instead of
row+colfam+colqual
order. This is required for the implementation of this iterator (to work in conjunction with the IntersectingIterator
) but
is a code-smell. This iterator should only be used at query time, never at compaction time.
The table structure should have the following form:
row term:docId => valueUsers configuring this iterator must set the option
COLUMNS_KEY
. This value is a comma-separated list of column families that should be "OR"'ed
together.
For example, given the following data and a value of or.iterator.columns="steve,bob"
in the iterator options map:
row1 bob:4 row1 george:2 row1 steve:3 row2 bob:9 row2 frank:8 row2 steve:12 row3 michael:15 row3 steve:20Would return:
row1 steve:3 row1 bob:4 row2 bob:9 row2 steve:12 row3 steve:20
Modifier and Type | Class and Description |
---|---|
protected static class |
OrIterator.TermSource |
OptionDescriber.IteratorOptions
Modifier and Type | Field and Description |
---|---|
static String |
COLUMNS_KEY |
Constructor and Description |
---|
OrIterator() |
Modifier and Type | Method and Description |
---|---|
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.
|
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.
|
void |
setTerms(SortedKeyValueIterator<Key,Value> source,
Collection<String> terms,
IteratorEnvironment env) |
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.
|
public static final String COLUMNS_KEY
public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
SortedKeyValueIterator
deepCopy
in interface SortedKeyValueIterator<Key,Value>
env
- IteratorEnvironment environment in which iterator is being run.public void setTerms(SortedKeyValueIterator<Key,Value> source, Collection<String> terms, IteratorEnvironment env)
public final 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<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.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.public final Key getTopKey()
SortedKeyValueIterator
For performance reasons, iterators reserve the right to reuse objects returned by getTopKey when SortedKeyValueIterator.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.
getTopKey
in interface SortedKeyValueIterator<Key,Value>
public final Value getTopValue()
SortedKeyValueIterator
For performance reasons, iterators reserve the right to reuse objects returned by getTopValue when SortedKeyValueIterator.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.
getTopValue
in interface SortedKeyValueIterator<Key,Value>
public final 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 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 © 2011–2018 The Apache Software Foundation. All rights reserved.