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Oracle® Coherence Java API Reference Release 3.7.1.0 E22843-01 |
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java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.filter.AbstractQueryRecorderFilter
com.tangosol.util.filter.LimitFilter
public class LimitFilter
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()
.
Constructor Summary | |
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LimitFilter() Default constructor (necessary for the ExternalizableLite interface). |
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LimitFilter(Filter filter, int cPageSize) Construct a limit filter. |
Method Summary | |
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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. page size and page number). |
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). |
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). |
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.filter.AbstractQueryRecorderFilter |
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explain, explain, trace, trace, trace, trace |
Methods inherited from class com.tangosol.util.BitHelper |
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countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString |
Constructor Detail |
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public LimitFilter()
public LimitFilter(Filter filter, int cPageSize)
filter
- the filter whose results this Filter truncatesMethod Detail |
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public boolean evaluate(java.lang.Object o)
evaluate
in interface Filter
o
- the object to testpublic boolean evaluateEntry(java.util.Map.Entry entry)
evaluateEntry
in interface EntryFilter
entry
- the Map Entry to evaluate; never nullpublic int calculateEffectiveness(java.util.Map mapIndexes, java.util.Set setKeys)
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.
calculateEffectiveness
in interface IndexAwareFilter
mapIndexes
- the available MapIndex
objects keyed by the related ValueExtractor; read-onlysetKeys
- the set of keys that will be filtered; read-onlypublic Filter applyIndex(java.util.Map mapIndexes, java.util.Set setKeys)
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.
applyIndex
in interface IndexAwareFilter
mapIndexes
- the available MapIndex
objects keyed by the related ValueExtractor; read-onlysetKeys
- the mutable set of keys that remain to be filteredFilter
object (which may be an EntryFilter
) that can be used to process the remaining keys, or null if no additional filter processing is necessarypublic Filter getFilter()
public int getPageSize()
public void setPageSize(int cPageSize)
cPageSize
- the page sizepublic int getPage()
public void setPage(int nPage)
nPage
- the page numberpublic java.util.Comparator getComparator()
This method is intended to be used only by query processors. Clients should not modify the content of this property.
public void setComparator(java.util.Comparator comparator)
This method is intended to be used only by query processors. Clients should not modify the content of this property.
comparator
- Comparator objectpublic java.lang.Object getTopAnchor()
This method is intended to be used only by query processors. Clients should not modify the content of this property.
public void setTopAnchor(java.lang.Object oAnchor)
This method is intended to be used only by query processors. Clients should not modify the content of this property.
oAnchor
- the top anchor objectpublic java.lang.Object getBottomAnchor()
This method is intended to be used only by query processors. Clients should not modify the content of this property.
public void setBottomAnchor(java.lang.Object oAnchor)
This method is intended to be used only by query processors. Clients should not modify the content of this property.
oAnchor
- the bottom anchor objectpublic java.lang.Object getCookie()
This method is intended to be used only by query processors. Clients should not modify the content of this property.
public void setCookie(java.lang.Object oCookie)
This method is intended to be used only by query processors. Clients should not modify the content of this property.
oCookie
- the cookie objectpublic void nextPage()
public void previousPage()
public java.lang.Object[] extractPage(java.lang.Object[] aEntry)
The returned array is guaranteed to iterate exactly in the same order as the original array.
aEntry
- an original array of entriespublic java.util.Set extractPage(java.util.Set set)
The returned set is guaranteed to iterate exactly in the same order as the original set.
set
- an original set of entriespublic java.lang.Object[] extractPage(java.util.Iterator iter)
iter
- an original entry iteratorpublic java.lang.String toString()
public java.lang.Object clone()
public void readExternal(java.io.DataInput in) throws java.io.IOException
readExternal
in interface ExternalizableLite
in
- the DataInput stream to read data from in order to restore the state of this objectjava.io.IOException
- if an I/O exception occursjava.io.NotActiveException
- if the object is not in its initial state, and therefore cannot be deserialized intopublic void writeExternal(java.io.DataOutput out) throws java.io.IOException
writeExternal
in interface ExternalizableLite
out
- the DataOutput stream to write the state of this object tojava.io.IOException
- if an I/O exception occurspublic void readExternal(PofReader in) throws java.io.IOException
readExternal
in interface PortableObject
in
- the PofReader from which to read the object's statejava.io.IOException
- if an I/O error occurspublic void writeExternal(PofWriter out) throws java.io.IOException
writeExternal
in interface PortableObject
out
- the PofWriter to which to write the object's statejava.io.IOException
- if an I/O error occurs
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Oracle® Coherence Java API Reference Release 3.7.1.0 E22843-01 |
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PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |