Package com.tangosol.util.filter

Class LimitFilter<T>

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.filter.AbstractQueryRecorderFilter<T>
com.tangosol.util.filter.LimitFilter<T>
All Implemented Interfaces:
ExternalizableLite, PortableObject, Filter<T>, EntryFilter<Object,T>, IndexAwareFilter<Object,T>, QueryRecorderFilter<T>, Serializable, Cloneable
public class LimitFilter<T> extends AbstractQueryRecorderFilter<T> implements EntryFilter<Object,T>, IndexAwareFilter<Object,T>, ExternalizableLite, PortableObject, Cloneable
Filter which truncates the results of another filter. This filter is a mutable object that is modified by the query processor. Clients are supposed to hold a reference to this filter and repetitively pass it to query methods after setting a desired page context calling setPage(int nPage), nextPage(), or previousPage().
Author:
gg 2002.12.06
See Also:

  • Constructor Details

    • LimitFilter

      public LimitFilter()
      Default constructor (necessary for the ExternalizableLite interface).

    • LimitFilter

      public LimitFilter(Filter<T> filter, int cPageSize)
      Construct a limit filter.
      Parameters:
      filter - the filter whose results this Filter truncates
      cPageSize - the page size

  • Method Details

    • evaluate

      public boolean evaluate(T o)
      Apply the test to the input argument.
      Specified by:
      evaluate in interface Filter<T>
      Parameters:
      o - the input argument to evaluate
      Returns:
      true if the input argument matches the filter, otherwise false

    • evaluateEntry

      public boolean evaluateEntry(Map.Entry entry)
      Apply the test to a Map Entry.
      Specified by:
      evaluateEntry in interface EntryFilter<Object,T>
      Parameters:
      entry - the Map Entry to evaluate; never null
      Returns:
      true if the test passes, false otherwise

    • calculateEffectiveness

      public int calculateEffectiveness(Map mapIndexes, Set setKeys)
      Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

      The returned value is an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys. An operation that requires no more than a single access to the index content (i.e. Equals, NotEquals) has an effectiveness of one. Evaluation of a single entry is assumed to have an effectiveness that depends on the index implementation and is usually measured as a constant number of the single operations. This number is referred to as evaluation cost.

      If the effectiveness of a filter evaluates to a number larger than the keySet.size() * <evaluation cost> then a user could avoid using the index and iterate through the keySet calling evaluate rather then applyIndex.

      Specified by:
      calculateEffectiveness in interface IndexAwareFilter<Object,T>
      Parameters:
      mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
      setKeys - the set of keys that will be filtered; read-only
      Returns:
      an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys

    • applyIndex

      public Filter applyIndex(Map mapIndexes, Set setKeys)
      Filter remaining keys using a Map of available indexes.

      The filter is responsible for removing all keys from the passed set of keys that the applicable indexes can prove should be filtered. If the filter does not fully evaluate the remaining keys using just the index information, it must return a filter (which may be an EntryFilter) that can complete the task using an iterating implementation. If, on the other hand, the filter does fully evaluate the remaining keys using just the index information, then it should return null to indicate that no further filtering is necessary.

      Specified by:
      applyIndex in interface IndexAwareFilter<Object,T>
      Parameters:
      mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
      setKeys - the mutable set of keys that remain to be filtered
      Returns:
      a Filter object (which may be an EntryFilter) that can be used to process the remaining keys, or null if no additional filter processing is necessary

    • getFilter

      public Filter<T> getFilter()
      Obtain the Filter whose results are truncated by this filter.
      Returns:
      the filter whose results are truncated by this filter

    • getPageSize

      public int getPageSize()
      Obtain the page size (expressed as a number of entries per page).
      Returns:
      the page size

    • setPageSize

      public void setPageSize(int cPageSize)
      Set the page size (expressed as a number of entries per page).
      Parameters:
      cPageSize - the page size

    • getPage

      public int getPage()
      Obtain a current page number (zero-based).
      Returns:
      the page number

    • setPage

      public void setPage(int nPage)
      Set the page number (zero-based). Setting the page number to zero will reset the filter's state.
      Parameters:
      nPage - the page number

    • getComparator

      public Comparator getComparator()
      Obtain the Comparator used to partition the entry values into pages.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Returns:
      the Comparator object

    • setComparator

      public void setComparator(Comparator comparator)
      Set the Comparator used to partition the values into pages.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Parameters:
      comparator - Comparator object

    • getTopAnchor

      public Object getTopAnchor()
      Obtain the top anchor object, which is the last value object on a previous page.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Returns:
      top anchor object

    • setTopAnchor

      public void setTopAnchor(Object oAnchor)
      Set the top anchor object.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Parameters:
      oAnchor - the top anchor object

    • getBottomAnchor

      public Object getBottomAnchor()
      Obtain the bottom anchor object, which is the last value object on the current page.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Returns:
      bottom anchor object

    • setBottomAnchor

      public void setBottomAnchor(Object oAnchor)
      Set the bottom anchor object.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Parameters:
      oAnchor - the bottom anchor object

    • getCookie

      public Object getCookie()
      Obtain the cookie object.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Returns:
      cookie object

    • setCookie

      public void setCookie(Object oCookie)
      Set the cookie object.

      This method is intended to be used only by query processors. Clients should not modify the content of this property.

      Parameters:
      oCookie - the cookie object

    • getBatchSize

      public int getBatchSize()
      Return the number of members query concurrently.
      Returns:
      batch size

    • setBatchSize

      public int setBatchSize(int cBatch)
      Set the number of members query concurrently.
      Parameters:
      cBatch - batch size
      Returns:
      the set batch size

    • nextPage

      public void nextPage()
      Switch to the next page.

    • previousPage

      public void previousPage()
      Switch to the previous page.

    • extractPage

      public Object[] extractPage(Object[] aEntry)
      Extract a subset of the specified array to fit the filter's parameters (i.e. page size and page number). If this filter has a comparator, the specified array is presumed to be sorted accordingly.

      The returned array is guaranteed to iterate exactly in the same order as the original array.

      Parameters:
      aEntry - an original array of entries
      Returns:
      an array of entries extracted accordingly to the filter parameters

    • extractPage

      public Set extractPage(Set set)
      Extract a subset of the specified set to fit the filter's parameters (i.e. page size and page number). If this filter has a comparator, the specified Set is presumed to be sorted accordingly.

      The returned set is guaranteed to iterate exactly in the same order as the original set.

      Parameters:
      set - an original set of entries
      Returns:
      a set of entries extracted accordingly to the filter parameters

    • extractPage

      public Object[] extractPage(Iterator iter)
      Extract a subset of the specified iterator to fit the filter's parameters (i.e. page size and page number). The returned array is guaranteed to iterate exactly in the same order as the original iterator.
      Parameters:
      iter - an original entry iterator
      Returns:
      an array of entries extracted accordingly to the filter parameters

    • toString

      public String toString()
      Return a human-readable description for this Filter.
      Overrides:
      toString in class Object
      Returns:
      a String description of the Filter

    • clone

      public Object clone()
      Clone this filter.
      Overrides:
      clone in class Object
      Returns:
      a clone of this filter

    • readExternal

      public void readExternal(DataInput in) throws IOException
      Restore the contents of this object by loading the object's state from the passed DataInput object.
      Specified by:
      readExternal in interface ExternalizableLite
      Parameters:
      in - the DataInput stream to read data from in order to restore the state of this object
      Throws:
      IOException - if an I/O exception occurs

    • writeExternal

      public void writeExternal(DataOutput out) throws IOException
      Save the contents of this object by storing the object's state into the passed DataOutput object.
      Specified by:
      writeExternal in interface ExternalizableLite
      Parameters:
      out - the DataOutput stream to write the state of this object to
      Throws:
      IOException - if an I/O exception occurs

    • readExternal

      public void readExternal(PofReader in) throws IOException
      Restore the contents of a user type instance by reading its state using the specified PofReader object.
      Specified by:
      readExternal in interface PortableObject
      Parameters:
      in - the PofReader from which to read the object's state
      Throws:
      IOException - if an I/O error occurs

    • writeExternal

      public void writeExternal(PofWriter out) throws IOException
      Save the contents of a POF user type instance by writing its state using the specified PofWriter object.
      Specified by:
      writeExternal in interface PortableObject
      Parameters:
      out - the PofWriter to which to write the object's state
      Throws:
      IOException - if an I/O error occurs