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

Class SeekingFilter

java.lang.Object
org.apache.accumulo.core.iterators.WrappingIterator
org.apache.accumulo.core.iterators.user.SeekingFilter
All Implemented Interfaces:
SortedKeyValueIterator<Key,Value>, YieldingKeyValueIterator<Key,Value>
Direct Known Subclasses:
CfCqSliceSeekingFilter
public abstract class SeekingFilter extends WrappingIterator
Base class for filters that can skip over key-value pairs which do not match their filter predicate. In addition to returning true/false to accept or reject a kv pair, subclasses can return an extra field which indicates how far the source iterator should be advanced. Note that the behaviour of the negate option is different from the Filter class. If a KV pair fails the subclass' filter predicate and negate is true, then the KV pair will pass the filter. However if the subclass advances the source past a bunch of KV pairs, all those pairs will be implicitly rejected and negate will have no effect.
See Also:

  • Field Details

  • Constructor Details

    • SeekingFilter

      public SeekingFilter()

  • Method Details

    • filter

      public abstract SeekingFilter.FilterResult filter(Key k, Value v)
      Subclasses must provide an implementation which examines the given key and value and determines (1) whether to accept the KV pair and (2) how far to advance the source iterator past the key.
      Parameters:
      k - a key
      v - a value
      Returns:
      indicating whether to pass or block the key, and how far the source iterator should be advanced.

    • getNextKeyHint

      public abstract Key getNextKeyHint(Key k, Value v)
      Whenever the subclass returns AdvanceResult.USE_HINT from its filter predicate, this method will be called to see how far to advance the source iterator. The return value must be a key which is greater than (sorts after) the input key. If the subclass never returns USE_HINT, this method will never be called and may safely return null.
      Parameters:
      k - a key
      v - a value
      Returns:
      as above

    • 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>
      Overrides:
      next in class WrappingIterator
      Throws:
      IOException - if an I/O error occurs.

    • 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>
      Overrides:
      hasTop in class WrappingIterator
      Returns:
      true if the iterator has more elements.

    • 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>
      Overrides:
      seek in class WrappingIterator
      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.

    • 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>
      Overrides:
      init in class WrappingIterator
      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.

    • 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 WrappingIterator
      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).

    • findTop

      protected void findTop() throws IOException
      Throws:
      IOException