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

Class IntersectingIterator

java.lang.Object
org.apache.accumulo.core.iterators.user.IntersectingIterator
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 to parallelize the search over all shardIDs. This iterator will *ignore* any columnFamilies passed to seek(Range, Collection, boolean) as it performs intersections over terms. Extending classes should override the IntersectingIterator.TermSource.seekColfams in their implementation's init(SortedKeyValueIterator, Map, IteratorEnvironment) method. An example of using the IntersectingIterator is available in the examples repo

  • Field Details

    • nullText

      protected org.apache.hadoop.io.Text nullText

    • sources

      protected IntersectingIterator.TermSource[] sources

    • currentPartition

      protected org.apache.hadoop.io.Text currentPartition

    • currentDocID

      protected org.apache.hadoop.io.Text currentDocID

    • topKey

      protected Key topKey

    • value

      protected Value value

  • Constructor Details

    • IntersectingIterator

      public IntersectingIterator()

  • Method Details

    • getPartition

      protected org.apache.hadoop.io.Text getPartition(Key key)

    • getTerm

      protected org.apache.hadoop.io.Text getTerm(Key key)

    • getDocID

      protected org.apache.hadoop.io.Text getDocID(Key key)

    • buildKey

      protected Key buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term)

    • buildKey

      protected Key buildKey(org.apache.hadoop.io.Text partition, org.apache.hadoop.io.Text term, org.apache.hadoop.io.Text docID)

    • buildFollowingPartitionKey

      protected Key buildFollowingPartitionKey(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>
      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).

    • 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 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 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 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.

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

    • advanceToIntersection

      protected void advanceToIntersection() throws IOException
      Throws:
      IOException

    • stringTopKey

      public static String stringTopKey(SortedKeyValueIterator<Key,Value> iter)

    • encodeColumns

      protected static String encodeColumns(org.apache.hadoop.io.Text[] columns)
      Returns:
      encoded columns

    • encodeBooleans

      protected static String encodeBooleans(boolean[] flags)
      Returns:
      encoded flags

    • decodeColumns

      protected static org.apache.hadoop.io.Text[] decodeColumns(String columns)

    • decodeBooleans

      protected static boolean[] decodeBooleans(String flags)
      Returns:
      decoded flags

    • 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 interface SortedKeyValueIterator<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.

    • 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>
      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.

    • setColumnFamilies

      public static void setColumnFamilies(IteratorSetting cfg, org.apache.hadoop.io.Text[] columns)
      Encode the columns to be used when iterating.

    • 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).