Package org.apache.accumulo.core.iterators

Class DevNull

java.lang.Object
org.apache.accumulo.core.iterators.DevNull
All Implemented Interfaces:
SortedKeyValueIterator<Key,Value>, YieldingKeyValueIterator<Key,Value>
public class DevNull extends Object implements SortedKeyValueIterator<Key,Value>
An iterator that is useful testing... for example if you want to test ingest performance w/o writing data to disk, insert this iterator for scan as follows using the accumulo shell. config -t ci -s table.iterator.minc.devnull=21,org.apache.accumulo.core.iterators.DevNull Could also make scans never return anything very quickly by adding it to the scan stack config -t ci -s table.iterator.scan.devnull=21,org.apache.accumulo.core.iterators.DevNull And to make major compactions never write anything config -t ci -s table.iterator.majc.devnull=21,org.apache.accumulo.core.iterators.DevNull

  • Constructor Details

    • DevNull

      public DevNull()

  • Method Details

    • 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.

    • 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.

    • 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.

    • 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.