Package org.apache.accumulo.core.iterators.user

Class IndexedDocIterator

  • All Implemented Interfaces:
    SortedKeyValueIterator<Key,​Value>, YieldingKeyValueIterator<Key,​Value>
    public class IndexedDocIterator
extends IntersectingIterator
    This iterator facilitates document-partitioned indexing. It is an example of extending the IntersectingIterator to customize the placement of the term and docID. As with the IntersectingIterator, documents are grouped together and indexed into a single row of an Accumulo table. This allows a tablet server to perform boolean AND operations on terms in the index. This iterator also stores the document contents in a separate column family in the same row so that the full document can be returned with each query. The table structure should have the following form: row: shardID, colfam: docColf\0doctype, colqual: docID, value: doc row: shardID, colfam: indexColf, colqual: term\0doctype\0docID\0info, value: (empty) When you configure this iterator with a set of terms, it will return only the docIDs and docs that appear with all of the specified terms. The result will have the following form: row: shardID, colfam: indexColf, colqual: doctype\0docID\0info, value: doc This iterator is commonly used with BatchScanner or AccumuloInputFormat, to parallelize the search over all shardIDs.

    • Field Detail

      • DEFAULT_INDEX_COLF

        public static final org.apache.hadoop.io.Text DEFAULT_INDEX_COLF

      • DEFAULT_DOC_COLF

        public static final org.apache.hadoop.io.Text DEFAULT_DOC_COLF

    • Constructor Detail

      • IndexedDocIterator

        public IndexedDocIterator()

    • Method Detail

      • buildKey

        protected Key buildKey​(org.apache.hadoop.io.Text partition,
                       org.apache.hadoop.io.Text term,
                       org.apache.hadoop.io.Text docID)
        Overrides:
        buildKey in class IntersectingIterator

      • buildKey

        protected Key buildKey​(org.apache.hadoop.io.Text partition,
                       org.apache.hadoop.io.Text term)
        Overrides:
        buildKey in class IntersectingIterator

      • parseDocID

        public static org.apache.hadoop.io.Text parseDocID​(Key key)

      • 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>
        Overrides:
        deepCopy in class IntersectingIterator
        Parameters:
        env - IteratorEnvironment environment in which iterator is being run.
        Returns:
        SortedKeyValueIterator a copy of this iterator (with the same source and settings).

      • 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 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>
        Overrides:
        seek in class IntersectingIterator
        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.

      • buildDocKey

        protected Key buildDocKey()

      • setIndexColf

        public static void setIndexColf​(IteratorSetting is,
                                String indexColf)
        A convenience method for setting the index column family.
        Parameters:
        is - IteratorSetting object to configure.
        indexColf - the index column family

      • setDocColfPrefix

        public static void setDocColfPrefix​(IteratorSetting is,
                                    String docColfPrefix)
        A convenience method for setting the document column family prefix.
        Parameters:
        is - IteratorSetting object to configure.
        docColfPrefix - the prefix of the document column family (colf will be of the form docColfPrefix\0doctype)

      • setColfs

        public static void setColfs​(IteratorSetting is,
                            String indexColf,
                            String docColfPrefix)
        A convenience method for setting the index column family and document column family prefix.
        Parameters:
        is - IteratorSetting object to configure.
        indexColf - the index column family
        docColfPrefix - the prefix of the document column family (colf will be of the form docColfPrefix\0doctype)