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Oracle® Coherence Java API Reference
v3.5.3
E15583-01
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## com.tangosol.util.filter
Class LimitFilter

    java.lang.Object
      com.tangosol.util.Base
          com.tangosol.util.BitHelper
              com.tangosol.util.ExternalizableHelper
                  com.tangosol.util.filter.LimitFilter

All Implemented Interfaces:
  ExternalizableLite, PortableObject, Filter, EntryFilter, IndexAwareFilter, java.io.Serializable, java.lang.Cloneable

    public class LimitFilter

extends ExternalizableHelper
implements Filter, EntryFilter, IndexAwareFilter, ExternalizableLite, PortableObject, java.lang.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)`, `nextPage()`, or `previousPage()`.

Author:
  gg 2002.12.06

Constructor Summary
`LimitFilter()` Default constructor (necessary for the ExternalizableLite interface).
`LimitFilter(Filter filter, int cPageSize)` Construct a limit filter.

Method Summary
`Filter` | `applyIndex(java.util.Map mapIndexes, java.util.Set setKeys)` Filter remaining keys using a Map of available indexes.
`int` | `calculateEffectiveness(java.util.Map mapIndexes, java.util.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.
`java.lang.Object` | `clone()` Clone this filter.
`boolean` | `evaluate(java.lang.Object o)` Apply the test to the object.
`boolean` | `evaluateEntry(java.util.Map.Entry entry)` Apply the test to a Map Entry.
`java.lang.Object[]` | `extractPage(java.util.Iterator iter)` Extract a subset of the specified iterator to fit the filter's parameters (i.e.
`java.lang.Object[]` | `extractPage(java.lang.Object[] aEntry)` Extract a subset of the specified array to fit the filter's parameters (i.e.
`java.util.Set` | `extractPage(java.util.Set set)` Extract a subset of the specified set to fit the filter's parameters (i.e.
`java.lang.Object` | `getBottomAnchor()` Obtain the bottom anchor object, which is the last value object on the current page.
`java.util.Comparator` | `getComparator()` Obtain the Comparator used to partition the entry values into pages.
`java.lang.Object` | `getCookie()` Obtain the cookie object.
`Filter` | `getFilter()` Obtain the Filter whose results are truncated by this filter.
`int` | `getPage()` Obtain a current page number (zero-based).
`int` | `getPageSize()` Obtain the page size (expressed as a number of entries per page).
`java.lang.Object` | `getTopAnchor()` Obtain the top anchor object, which is the last value object on a previous page.
`void` | `nextPage()` Switch to the next page.
`void` | `previousPage()` Switch to the previous page.
`void` | `readExternal(java.io.DataInput in)` Restore the contents of this object by loading the object's state from the passed DataInput object.
`void` | `readExternal(PofReader in)` Restore the contents of a user type instance by reading its state using the specified PofReader object.
`void` | `setBottomAnchor(java.lang.Object oAnchor)` Set the bottom anchor object.
`void` | `setComparator(java.util.Comparator comparator)` Set the Comparator used to partition the values into pages.
`void` | `setCookie(java.lang.Object oCookie)` Set the cookie object.
`void` | `setPage(int nPage)` Set the page number (zero-based).
`void` | `setPageSize(int cPageSize)` Set the page size (expressed as a number of entries per page).
`void` | `setTopAnchor(java.lang.Object oAnchor)` Set the top anchor object.
`java.lang.String` | `toString()` Return a human-readable description for this Filter.
`void` | `writeExternal(java.io.DataOutput out)` Save the contents of this object by storing the object's state into the passed DataOutput object.
`void` | `writeExternal(PofWriter out)` Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Methods inherited from class com.tangosol.util.BitHelper
`countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString`

Constructor Detail

### LimitFilter

    public LimitFilter()

  Default constructor (necessary for the ExternalizableLite interface).

### LimitFilter

    public LimitFilter(Filter filter,
                       int cPageSize)

  Construct a limit filter.

  Parameters:
    `filter` - the filter whose results this Filter truncates

Method Detail

### evaluate

    public boolean evaluate(java.lang.Object o)

  Apply the test to the object.

  Specified by:
    `evaluate` in interface `Filter`
  Parameters:
    `o` - the object to test
  Returns:
    true if the test passes, false otherwise

### evaluateEntry

    public boolean evaluateEntry(java.util.Map.Entry entry)

  Apply the test to a Map Entry.

  Specified by:
    `evaluateEntry` in interface `EntryFilter`
  Parameters:
    `entry` - the Map Entry to evaluate; never null
  Returns:
    true if the test passes, false otherwise

### calculateEffectiveness

    public int calculateEffectiveness(java.util.Map mapIndexes,
                                      java.util.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`
  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(java.util.Map mapIndexes,
                             java.util.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`
  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 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 java.util.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(java.util.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 java.lang.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(java.lang.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 java.lang.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(java.lang.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 java.lang.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(java.lang.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

### nextPage

    public void nextPage()

  Switch to the next page.

### previousPage

    public void previousPage()

  Switch to the previous page.

### extractPage

    public java.lang.Object[] extractPage(java.lang.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 java.util.Set extractPage(java.util.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 java.lang.Object[] extractPage(java.util.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 java.lang.String toString()

  Return a human-readable description for this Filter.

  Returns:
    a String description of the Filter

### clone

    public java.lang.Object clone()

  Clone this filter.

  Returns:
    a clone of this filter

### readExternal

    public void readExternal(java.io.DataInput in)
                      throws java.io.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:
    `java.io.IOException` - if an I/O exception occurs
    `java.io.NotActiveException` - if the object is not in its initial state, and therefore cannot be deserialized into

### writeExternal

    public void writeExternal(java.io.DataOutput out)
                       throws java.io.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:
    `java.io.IOException` - if an I/O exception occurs

### readExternal

    public void readExternal(PofReader in)
                      throws java.io.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:
    `java.io.IOException` - if an I/O error occurs

### writeExternal

    public void writeExternal(PofWriter out)
                       throws java.io.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:
    `java.io.IOException` - if an I/O error occurs

Overview | Package | Class | Tree | Index | Help

Oracle® Coherence Java API Reference
v3.5.3
E15583-01
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

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