Class LimitFilter

IFilter which truncates the results of another filter.

Inheritance

object

LimitFilter

Implements

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Tangosol.Util.Filter

Assembly: Coherence.dll

Syntax

public class LimitFilter : IIndexAwareFilter, IEntryFilter, IFilter, IPortableObject

Remarks

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.

Constructors

LimitFilter()

Default constructor.

Declaration

public LimitFilter()

LimitFilter(IFilter, int)

Construct a limit filter.

Declaration

public LimitFilter(IFilter filter, int pageSize)

Parameters

Type	Name	Description
IFilter	filter	The filter whose results this filter truncates.
int	pageSize	Page size.

Properties

BottomAnchor

Gets or sets the bottom anchor object, which is the last value object on the current page.

Declaration

public virtual object BottomAnchor { get; set; }

Property Value

Type	Description
object	Bottom anchor object.

Remarks

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

Comparer

Gets or sets the IComparer used to partition the entry values into pages.

Declaration

public virtual IComparer Comparer { get; set; }

Property Value

Type	Description
IComparer	The IComparer object.

Remarks

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

Cookie

Gets or sets the cookie object.

Declaration

public virtual object Cookie { get; set; }

Property Value

Type	Description
object	Cookie object.

Remarks

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

Filter

Gets the IFilter whose results are truncated by this filter.

Declaration

public virtual IFilter Filter { get; }

Property Value

Type	Description
IFilter	The filter whose results are truncated by this filter.

Page

Gets or sets current page number (zero-based).

Declaration

public virtual int Page { get; set; }

Property Value

Type	Description
int	The current page number.

PageSize

Gets or sets the page size (expressed as a number of entries per page).

Declaration

public virtual int PageSize { get; set; }

Property Value

Type	Description
int	The page size.

TopAnchor

Gets or sets the top anchor object, which is the last value object on a previous page.

Declaration

public virtual object TopAnchor { get; set; }

Property Value

Type	Description
object	Top anchor object.

Remarks

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

Methods

ApplyIndex(IDictionary, ICollection)

Filter remaining keys using an IDictionary of available indexes.

Declaration

public IFilter ApplyIndex(IDictionary indexes, ICollection keys)

Parameters

Type	Name	Description
IDictionary	indexes	The available ICacheIndex objects keyed by the related IValueExtractor; read-only.
ICollection	keys	The mutable set of keys that remain to be filtered.

Returns

Type	Description
IFilter	An IFilter object that can be used to process the remaining keys, or `null` if no additional filter processing is necessary.

Remarks

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 IEntryFilter) 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.

CalculateEffectiveness(IDictionary, ICollection)

Given an IDictionary of available indexes, determine if this IIndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

Declaration

public int CalculateEffectiveness(IDictionary indexes, ICollection keys)

Parameters

Type	Name	Description
IDictionary	indexes	The available ICacheIndex objects keyed by the related IValueExtractor; read-only.
ICollection	keys	The set of keys that will be filtered; read-only.

Returns

Type	Description
int	An effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys.

Remarks

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 keys.size() then a user could avoid using the index and iterate through the keys calling Evaluate rather than ApplyIndex.

Evaluate(object)

Apply the test to the object.

Declaration

public virtual bool Evaluate(object o)

Parameters

Type	Name	Description
object	o	An object to which the test is applied.

Returns

Type	Description
bool	true if the test passes, false otherwise.

EvaluateEntry(ICacheEntry)

Apply the test to an ICacheEntry.

Declaration

public virtual bool EvaluateEntry(ICacheEntry entry)

Parameters

Type	Name	Description
ICacheEntry	entry	The ICacheEntry to evaluate; never `null`.

Returns

Type	Description
bool	true if the test passes, false otherwise.

ExtractPage(ICollection)

Extract a subset of the specified set to fit the filter's parameters (i.e. page size and page number).

Declaration

public virtual ICollection ExtractPage(ICollection entries)

Parameters

Type	Name	Description
ICollection	entries	An original set of entries.

Returns

Type	Description
ICollection	A set of entries extracted accordingly to the filter parameters.

Remarks

If this filter has a comparator, the specified ICollection is presumed to be sorted accordingly.

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

ExtractPage(IEnumerator)

Extract a subset of the specified iterator to fit the filter's parameters (i.e. page size and page number).

Declaration

public virtual object[] ExtractPage(IEnumerator iter)

Parameters

Type	Name	Description
IEnumerator	iter	An original entry iterator.

Returns

Type	Description
object[]	An array of entries extracted accordingly to the filter parameters

Remarks

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

ExtractPage(object[])

Extract a subset of the specified array to fit the filter's parameters (i.e. page size and page number).

Declaration

public virtual object[] ExtractPage(object[] entries)

Parameters

Type	Name	Description
object[]	entries	An original array of entries.

Returns

Type	Description
object[]	An array of entries extracted accordingly to the filter parameters.

Remarks

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.

NextPage()

Switch to the next page.

Declaration

public virtual void NextPage()

PreviousPage()

Switch to the previous page.

Declaration

public virtual void PreviousPage()

ReadExternal(IPofReader)

Restore the contents of a user type instance by reading its state using the specified IPofReader object.

Declaration

public virtual void ReadExternal(IPofReader reader)

Parameters

Type	Name	Description
IPofReader	reader	The IPofReader from which to read the object's state.

Exceptions

Type	Condition
IOException	If an I/O error occurs.

ToString()

Return a human-readable description for this LimitFilter.

Declaration

public override string ToString()

Returns

Type	Description
string	A string description of the LimitFilter.

Overrides

object.ToString()

WriteExternal(IPofWriter)

Save the contents of a POF user type instance by writing its state using the specified IPofWriter object.

Declaration

public virtual void WriteExternal(IPofWriter writer)

Parameters

Type	Name	Description
IPofWriter	writer	The IPofWriter to which to write the object's state.

Exceptions

Type	Condition
IOException	If an I/O error occurs.

Implements

IIndexAwareFilter

IEntryFilter

IFilter

IPortableObject