Class RowEncodingIterator
- All Implemented Interfaces:
OptionDescriber
,SortedKeyValueIterator<Key,
,Value> YieldingKeyValueIterator<Key,
Value>
- Direct Known Subclasses:
WholeRowIterator
For an example implementation, see WholeRowIterator
.
One caveat is that when seeking in the WholeRowIterator using a range that starts at a non-inclusive first key in a row, (e.g. seek(new Range(new Key(new Text("row")),false,...),...)) this iterator will skip to the next row. This is done in order to prevent repeated scanning of the same row when system automatically creates ranges of that form, which happens in the case of the client calling continueScan, or in the case of the tablet server continuing a scan after swapping out sources.
To regain the original key/value pairs of the row, call the rowDecoder function on the key/value pair that this iterator returned.
- See Also:
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Nested Class Summary
Nested classes/interfaces inherited from interface org.apache.accumulo.core.iterators.OptionDescriber
OptionDescriber.IteratorOptions
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionCreates a deep copy of this iterator as though seek had not yet been called.Gets an iterator options object that contains information needed to configure this iterator.protected boolean
Returns top key.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.rowDecoder
(Key rowKey, Value rowValue) Given a value generated by the rowEncoder implementation, recreate the original Key, Value pairs.abstract Value
rowEncoder
(List<Key> keys, List<Value> values) Take a stream of keys and values.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.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.Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.apache.accumulo.core.iterators.YieldingKeyValueIterator
enableYielding
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Field Details
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MAX_BUFFER_SIZE_OPT
- See Also:
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sourceIter
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Constructor Details
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RowEncodingIterator
public RowEncodingIterator()
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Method Details
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rowDecoder
Given a value generated by the rowEncoder implementation, recreate the original Key, Value pairs.- Throws:
IOException
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rowEncoder
Take a stream of keys and values. Return values in the same order encoded such that all portions of the key (except for the row value) and the original value are encoded in some way.- Throws:
IOException
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deepCopy
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, provided by Accumulo itself and is expected to be non-null.- Returns:
SortedKeyValueIterator
a copy of this iterator (with the same source and settings).
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filter
- Parameters:
currentRow
- All keys have this in their row portion (do not modify!).keys
- One key for each key in the row, ordered as they are given by the source iterator (do not modify!).values
- One value for each key in keys, ordered to correspond to the ordering in keys (do not modify!).- Returns:
- true if we want to keep the row, false if we want to skip it
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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
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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init
public void init(SortedKeyValueIterator<Key, Value> source, Map<String, throws IOExceptionString> options, IteratorEnvironment env) 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, provided by Accumulo itself and is expected to be non-null.- Throws:
IOException
- unused.
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describeOptions
Description copied from interface:OptionDescriber
Gets an iterator options object that contains information needed to configure this iterator. This object will be used by the accumulo shell to prompt the user to input the appropriate information.- Specified by:
describeOptions
in interfaceOptionDescriber
- Returns:
- an iterator options object
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validateOptions
Description copied from interface:OptionDescriber
Check to see if an options map contains all options required by an iterator and that the option values are in the expected formats.- Specified by:
validateOptions
in interfaceOptionDescriber
- Parameters:
options
- a map of option names to option values- Returns:
- true if options are valid, false otherwise (IllegalArgumentException preferred)
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next
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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seek
public void seek(Range range, Collection<ByteSequence> columnFamilies, 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.columnFamilies
-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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