Package org.apache.accumulo.core.iterators

Class OrIterator

  • All Implemented Interfaces:
    OptionDescriber, SortedKeyValueIterator<Key,​Value>, YieldingKeyValueIterator<Key,​Value>
    public class OrIterator
extends Object
implements SortedKeyValueIterator<Key,​Value>, OptionDescriber
    An iterator that provides a sorted-iteration of column qualifiers for a set of column families in a row. It is important to note that this iterator does not adhere to the contract set forth by the 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 => value
    Users 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:20
    Would return: 
     row1 steve:3
 row1 bob:4
 row2 bob:9
 row2 steve:12
 row3 steve:20

    • Constructor Detail

      • OrIterator

        public OrIterator()

    • Method Detail

      • 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 interface SortedKeyValueIterator<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).

      • next

        public final 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 interface SortedKeyValueIterator<Key,​Value>
        Throws:
        IOException - if an I/O error occurs.

      • 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 after 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.
        Specified by:
        seek in interface SortedKeyValueIterator<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.

      • getTopKey

        public final 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 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.

        Specified by:
        getTopKey in interface SortedKeyValueIterator<Key,​Value>
        Returns:
        K

      • getTopValue

        public final 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 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.

        Specified by:
        getTopValue in interface SortedKeyValueIterator<Key,​Value>
        Returns:
        V

      • hasTop

        public final 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 interface SortedKeyValueIterator<Key,​Value>
        Returns:
        true if the iterator has more elements.

      • describeOptions

        public OptionDescriber.IteratorOptions 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 interface OptionDescriber
        Returns:
        an iterator options object

      • validateOptions

        public boolean validateOptions​(Map<String,​String> options)
        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 interface OptionDescriber
        Parameters:
        options - a map of option names to option values
        Returns:
        true if options are valid, false otherwise (IllegalArgumentException preferred)