Aggregate

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.FunctionCall
  - - net.sf.saxon.functions.SystemFunction
    - - net.sf.saxon.functions.Aggregate

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
public class Aggregate
extends SystemFunction
```
This class implements the sum(), avg(), count() functions,

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

static int AVG

static int COUNT

static int SUM
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
- Fields inherited from class net.sf.saxon.expr.FunctionCall
  argument
- Fields inherited from class net.sf.saxon.functions.SystemFunction
  operation

Fields
Modifier and Type	Field	Description
`static int`	`AVG`
`static int`	`COUNT`
`static int`	`SUM`

Constructor Summary

Constructors
Constructor Description

Aggregate()

Constructors
Constructor	Description
`Aggregate()`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static AtomicValue`	`average(SequenceIterator iter, XPathContext context, javax.xml.transform.SourceLocator location)`	Calculate average
`void`	`checkArguments(ExpressionVisitor visitor)`	Static analysis: prevent sorting of the argument
`int`	`computeCardinality()`	Determine the cardinality of the function.
`static int`	`count(SequenceIterator iter)`	Get the number of items in a sequence identified by a SequenceIterator
`Item`	`evaluateItem(XPathContext context)`	Evaluate the function
`ItemType`	`getItemType(TypeHierarchy th)`	Determine the item type of the value returned by the function
`static boolean`	`isCountFunction(Expression exp)`	Determine whether a given expression is a call to the count() function
`static AtomicValue`	`total(SequenceIterator iter, XPathContext context, javax.xml.transform.SourceLocator location)`	Calculate the total of a sequence.

Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterate, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class net.sf.saxon.expr.FunctionCall
addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, addDocToPathMap, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getRequiredType, makeSystemFunction, optimize, setDetails, useContextItemAsDefault

- Field Detail
  - SUM
```
public static final int SUM
```
    See Also:
    
    Constant Field Values
  - AVG
```
public static final int AVG
```
    See Also:
    
    Constant Field Values
  - COUNT
```
public static final int COUNT
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Aggregate
```
public Aggregate()
```
- Method Detail
  - checkArguments
```
public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException
```
    Static analysis: prevent sorting of the argument
    
    Overrides:
    
    checkArguments in class SystemFunction
    
    Parameters:
    
    visitor - the expression visitor
    
    Throws:
    
    XPathException
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Determine the item type of the value returned by the function
    
    Overrides:
    
    getItemType in class SystemFunction
    
    Parameters:
    
    th - the type hierarchy cache
    
    Returns:
    
    a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)
  - computeCardinality
```
public int computeCardinality()
```
    Determine the cardinality of the function.
    
    Overrides:
    
    computeCardinality in class SystemFunction
    
    Returns:
    
    the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate the function
    
    Specified by:
    
    evaluateItem in interface EvaluableItem
    
    Overrides:
    
    evaluateItem in class Expression
    
    Parameters:
    
    context - The context in which the expression is to be evaluated
    
    Returns:
    
    the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - total
```
public static AtomicValue total(SequenceIterator iter,
                                XPathContext context,
                                javax.xml.transform.SourceLocator location)
                         throws XPathException
```
    Calculate the total of a sequence.
    
    Parameters:
    
    iter - iterator over the items to be totalled
    
    context - the XPath dynamic context
    
    location - location of the expression in the source for diagnostics
    
    Returns:
    
    the total, according to the rules of the XPath sum() function, but returning null if the sequence is empty. (It's then up to the caller to decide what the correct result is for an empty sequence.
    
    Throws:
    
    XPathException
  - average
```
public static AtomicValue average(SequenceIterator iter,
                                  XPathContext context,
                                  javax.xml.transform.SourceLocator location)
                           throws XPathException
```
    Calculate average
    
    Parameters:
    
    iter - iterator over the items to be totalled
    
    context - the XPath dynamic context
    
    location - location of the expression in the source for diagnostics
    
    Returns:
    
    the average of the values
    
    Throws:
    
    XPathException
  - count
```
public static int count(SequenceIterator iter)
                 throws XPathException
```
    Get the number of items in a sequence identified by a SequenceIterator
    
    Parameters:
    
    iter - The SequenceIterator. This method moves the current position of the supplied iterator; if this isn't safe, make a copy of the iterator first by calling getAnother(). The supplied iterator must be positioned before the first item (there must have been no call on next()).
    
    Returns:
    
    the number of items in the underlying sequence
    
    Throws:
    
    XPathException - if a failure occurs reading the input sequence
  - isCountFunction
```
public static boolean isCountFunction(Expression exp)
```
    Determine whether a given expression is a call to the count() function
    
    Parameters:
    
    exp - an expression to be examined
    
    Returns:
    
    true if the expression is a call to the count() function

Class Aggregate

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

Fields inherited from class net.sf.saxon.expr.FunctionCall

Fields inherited from class net.sf.saxon.functions.SystemFunction

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.Expression

Methods inherited from class net.sf.saxon.expr.FunctionCall

Methods inherited from class java.lang.Object

Methods inherited from class net.sf.saxon.functions.SystemFunction

Field Detail

SUM

AVG

COUNT

Constructor Detail

Aggregate

Method Detail

checkArguments

getItemType

computeCardinality

evaluateItem

total

average

count

isCountFunction