Class IntersectingIterator
- java.lang.Object
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- org.apache.accumulo.core.iterators.user.IntersectingIterator
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- All Implemented Interfaces:
SortedKeyValueIterator<Key,Value>
,YieldingKeyValueIterator<Key,Value>
- Direct Known Subclasses:
IndexedDocIterator
public class IntersectingIterator extends Object implements SortedKeyValueIterator<Key,Value>
This iterator facilitates document-partitioned indexing. It involves grouping a set of documents together and indexing those documents into a single row of an Accumulo table. This allows a tablet server to perform boolean AND operations on terms in the index. The table structure should have the following form: row: shardID, colfam: term, colqual: docID When you configure this iterator with a set of terms (column families), it will return only the docIDs that appear with all of the specified terms. The result will have an empty column family, as follows: row: shardID, colfam: (empty), colqual: docID This iterator is commonly used with BatchScanner or AccumuloInputFormat, to parallelize the search over all shardIDs. This iterator will *ignore* any columnFamilies passed toseek(Range, Collection, boolean)
as it performs intersections over terms. Extending classes should override theIntersectingIterator.TermSource.seekColfams
in their implementation'sinit(SortedKeyValueIterator, Map, IteratorEnvironment)
method. An example of using the IntersectingIterator is available at https://github.com/apache/accumulo-examples/blob/master/docs/shard.md
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
IntersectingIterator.TermSource
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Field Summary
Fields Modifier and Type Field Description protected org.apache.hadoop.io.Text
currentDocID
protected org.apache.hadoop.io.Text
currentPartition
protected org.apache.hadoop.io.Text
nullText
protected IntersectingIterator.TermSource[]
sources
protected Key
topKey
protected Value
value
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Constructor Summary
Constructors Constructor Description IntersectingIterator()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description protected void
advanceToIntersection()
protected Key
buildFollowingPartitionKey(Key key)
protected Key
buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term)
protected Key
buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term, org.apache.hadoop.io.Text docID)
protected static boolean[]
decodeBooleans(String flags)
protected static org.apache.hadoop.io.Text[]
decodeColumns(String columns)
SortedKeyValueIterator<Key,Value>
deepCopy(IteratorEnvironment env)
Creates a deep copy of this iterator as though seek had not yet been called.protected static String
encodeBooleans(boolean[] flags)
protected static String
encodeColumns(org.apache.hadoop.io.Text[] columns)
protected org.apache.hadoop.io.Text
getDocID(Key key)
protected org.apache.hadoop.io.Text
getPartition(Key key)
protected org.apache.hadoop.io.Text
getTerm(Key key)
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> seekColumnFamilies, boolean inclusive)
Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns.static void
setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns)
Encode the columns to be used when iterating.static void
setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns, boolean[] notFlags)
Encode columns and NOT flags indicating which columns should be negated (docIDs will be excluded if matching negated columns, instead of included).static String
stringTopKey(SortedKeyValueIterator<Key,Value> iter)
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator
enableYielding
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Field Detail
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nullText
protected org.apache.hadoop.io.Text nullText
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sources
protected IntersectingIterator.TermSource[] sources
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currentPartition
protected org.apache.hadoop.io.Text currentPartition
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currentDocID
protected org.apache.hadoop.io.Text currentDocID
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topKey
protected Key topKey
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value
protected Value value
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Method Detail
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getPartition
protected org.apache.hadoop.io.Text getPartition(Key key)
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getTerm
protected org.apache.hadoop.io.Text getTerm(Key key)
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getDocID
protected org.apache.hadoop.io.Text getDocID(Key key)
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buildKey
protected Key buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term)
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buildKey
protected Key buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term, org.apache.hadoop.io.Text docID)
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deepCopy
public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env)
Description copied from interface:SortedKeyValueIterator
Creates a deep copy of this iterator as though seek had not yet been called. init should be called on an iterator before deepCopy is called. init should not need to be called on the copy that is returned by deepCopy; that is, when necessary init should be called in the deepCopy method on the iterator it returns. The behavior is unspecified if init is called after deepCopy either on the original or the copy. A proper implementation would call deepCopy on the source.- Specified by:
deepCopy
in interfaceSortedKeyValueIterator<Key,Value>
- Parameters:
env
-IteratorEnvironment
environment in which iterator is being run.- Returns:
SortedKeyValueIterator
a copy of this iterator (with the same source and settings).
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getTopKey
public Key getTopKey()
Description copied from interface:SortedKeyValueIterator
Returns top key. Can be called 0 or more times without affecting behavior of next() or hasTop(). Note that in minor compaction scope and in non-full major compaction scopes the iterator may see deletion entries. These entries should be preserved by all iterators except ones that are strictly scan-time iterators that will never be configured for the minc or majc scopes. Deletion entries are only removed during full major compactions.For performance reasons, iterators reserve the right to reuse objects returned by
getTopKey
whenSortedKeyValueIterator.next()
is called, changing the data that the object references. Iterators that need to save an object returned bygetTopKey
ought to copy the object's data into a new object in order to avoid aliasing bugs.- Specified by:
getTopKey
in interfaceSortedKeyValueIterator<Key,Value>
- Returns:
K
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getTopValue
public Value getTopValue()
Description copied from interface:SortedKeyValueIterator
Returns top value. Can be called 0 or more times without affecting behavior of next() or hasTop().For performance reasons, iterators reserve the right to reuse objects returned by
getTopValue
whenSortedKeyValueIterator.next()
is called, changing the underlying data that the object references. Iterators that need to save an object returned bygetTopValue
ought to copy the object's data into a new object in order to avoid aliasing bugs.- Specified by:
getTopValue
in interfaceSortedKeyValueIterator<Key,Value>
- Returns:
V
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hasTop
public boolean hasTop()
Description copied from interface:SortedKeyValueIterator
Returns true if the iterator has more elements. Note that if this iterator has yielded (@see YieldingKeyValueIterator.enableYielding(YieldCallback)), this this method must return false.- Specified by:
hasTop
in interfaceSortedKeyValueIterator<Key,Value>
- Returns:
true
if the iterator has more elements.
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next
public void next() throws IOException
Description copied from interface:SortedKeyValueIterator
Advances to the next K,V pair. Note that in minor compaction scope and in non-full major compaction scopes the iterator may see deletion entries. These entries should be preserved by all iterators except ones that are strictly scan-time iterators that will never be configured for the minc or majc scopes. Deletion entries are only removed during full major compactions.- Specified by:
next
in interfaceSortedKeyValueIterator<Key,Value>
- Throws:
IOException
- if an I/O error occurs.
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advanceToIntersection
protected void advanceToIntersection() throws IOException
- Throws:
IOException
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stringTopKey
public static String stringTopKey(SortedKeyValueIterator<Key,Value> iter)
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encodeColumns
protected static String encodeColumns(org.apache.hadoop.io.Text[] columns)
- Returns:
- encoded columns
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encodeBooleans
protected static String encodeBooleans(boolean[] flags)
- Returns:
- encoded flags
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decodeColumns
protected static org.apache.hadoop.io.Text[] decodeColumns(String columns)
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decodeBooleans
protected static boolean[] decodeBooleans(String flags)
- Returns:
- decoded flags
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init
public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options, IteratorEnvironment env) throws IOException
Description copied from interface:SortedKeyValueIterator
Initializes the iterator. Data should not be read from the source in this method.- Specified by:
init
in interfaceSortedKeyValueIterator<Key,Value>
- Parameters:
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.- Throws:
IOException
- unused.
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seek
public void seek(Range range, Collection<ByteSequence> seekColumnFamilies, boolean inclusive) throws IOException
Description copied from interface:SortedKeyValueIterator
Seeks to the first key in the Range, restricting the resulting K,V pairs to those with the specified columns. An iterator does not have to stop at the end of the range. The whole range is provided so that iterators can make optimizations. Seek may be called multiple times with different parameters afterSortedKeyValueIterator.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 therange
. In an Accumulo instance in which multiple locality groups exist for a table, it is important to ensure thatcolumnFamilies
is properly set to the minimum required column families to ensure that data from separate locality groups is not inadvertently read.- Specified by:
seek
in interfaceSortedKeyValueIterator<Key,Value>
- Parameters:
range
-Range
of keys to iterate over.seekColumnFamilies
-Collection
of column families to include or exclude.inclusive
-boolean
that indicates whether to include (true) or exclude (false) column families.- Throws:
IOException
- if an I/O error occurs.
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setColumnFamilies
public static void setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns)
Encode the columns to be used when iterating.
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setColumnFamilies
public static void setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns, boolean[] notFlags)
Encode columns and NOT flags indicating which columns should be negated (docIDs will be excluded if matching negated columns, instead of included).
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