com.espertech.esper.epl.expression.baseagg
Class ExprAggregateNodeBase

java.lang.Object
  com.espertech.esper.epl.expression.core.ExprNodeBase
      com.espertech.esper.epl.expression.baseagg.ExprAggregateNodeBase

All Implemented Interfaces:

ExprAggregateNode, ExprEvaluator, ExprNode, ExprValidator, MetaDefItem, java.io.Serializable

Direct Known Subclasses:

ExprAggCountMinSketchNode, ExprAggMultiFunctionLinearAccessNode, ExprAggMultiFunctionSortedMinMaxByNode, ExprAvedevNode, ExprAvgNode, ExprCountEverNode, ExprCountNode, ExprFirstEverNode, ExprLastEverNode, ExprLeavingAggNode, ExprMedianNode, ExprMinMaxAggrNode, ExprNthAggNode, ExprPlugInAggFunctionFactoryNode, ExprPlugInAggMultiFunctionNode, ExprRateAggNode, ExprStddevNode, ExprSumNode

public abstract class ExprAggregateNodeBase
extends ExprNodeBase
implements ExprEvaluator, ExprAggregateNode

Base expression node that represents an aggregation function such as 'sum' or 'count'.

In terms of validation each concrete aggregation node must implement it's own validation.

In terms of evaluation this base class will ask the assigned AggregationResultFuture for the current state, using a column number assigned to the node.

Concrete subclasses must supply an aggregation state prototype node AggregationMethod that reflects each group's (there may be group-by critera) current aggregation state.

See Also:

Serialized Form

Field Summary

protected AggregationResultFuture	aggregationResultFuture
protected int	column
protected boolean	isDistinct Indicator for whether the aggregation is distinct - i.e.
protected ExprAggregateLocalGroupByDesc	optionalAggregateLocalGroupByDesc
protected ExprNode[]	positionalParams

Constructor Summary

protected

ExprAggregateNodeBase(boolean distinct) Ctor.

Method Summary

boolean	equalsNode(ExprNode node) Return true if a expression node semantically equals the current node, or false if not.
protected abstract boolean	equalsNodeAggregateMethodOnly(ExprAggregateNode node) Return true if a expression aggregate node semantically equals the current node, or false if not.
java.lang.Object	evaluate(EventBean[] events, boolean isNewData, ExprEvaluatorContext exprEvaluatorContext) Evaluate event tuple and return result.
abstract java.lang.String	getAggregationFunctionName() Returns the aggregation function name for representation in a generate expression string.
ExprEvaluator	getExprEvaluator()
AggregationMethodFactory	getFactory() Returns the aggregation state factory for use in grouping aggregation states per group-by keys.
ExprAggregateLocalGroupByDesc	getOptionalLocalGroupBy()
ExprNode[]	getPositionalParams()
ExprPrecedenceEnum	getPrecedence() Returns precedence.
java.lang.Class	getType() Returns the type that the node's evaluate method returns an instance of.
boolean	isConstantResult() Returns true if the expression node's evaluation value doesn't depend on any events data, as must be determined at validation time, which is bottom-up and therefore reliably allows each node to determine constant value.
boolean	isDistinct() Returns true if the aggregation node is only aggregatig distinct values, or false if aggregating all values.
protected boolean	isExprTextWildcardWhenNoParams()
protected ExprValidationException	makeExceptionExpectedParamNum(int lower, int upper)
void	setAggregationResultFuture(AggregationResultFuture aggregationResultFuture, int column) Assigns to the node the future which can be queried for the current aggregation state at evaluation time.
void	toPrecedenceFreeEPL(java.io.StringWriter writer)
ExprNode	validate(ExprValidationContext validationContext)
protected abstract AggregationMethodFactory	validateAggregationChild(ExprValidationContext validationContext) Gives the aggregation node a chance to validate the sub-expression types.
void	validateFilter(ExprEvaluator filterEvaluator)
protected java.lang.Class	validateNumericChildAllowFilter(boolean hasFilter) For use by implementing classes, validates the aggregation node expecting a single numeric-type child node.
void	validatePositionals()

Methods inherited from class com.espertech.esper.epl.expression.core.ExprNodeBase

accept, accept, acceptChildnodes, addChildNode, addChildNodes, addChildNodeToFront, getChildNodes, replaceUnlistedChildNode, setChildNode, setChildNodes, toEPL

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.espertech.esper.epl.expression.core.ExprNode

accept, accept, acceptChildnodes, addChildNode, addChildNodes, getChildNodes, replaceUnlistedChildNode, setChildNode, setChildNodes, toEPL

Field Detail

aggregationResultFuture

protected transient AggregationResultFuture aggregationResultFuture

column

protected int column

optionalAggregateLocalGroupByDesc

protected ExprAggregateLocalGroupByDesc optionalAggregateLocalGroupByDesc

positionalParams

protected ExprNode[] positionalParams

isDistinct

protected boolean isDistinct

Indicator for whether the aggregation is distinct - i.e. only unique values are considered.

Constructor Detail

ExprAggregateNodeBase

protected ExprAggregateNodeBase(boolean distinct)

Ctor.

Parameters:

distinct - - sets the flag indicatating whether only unique values should be aggregated

Method Detail

getAggregationFunctionName

public abstract java.lang.String getAggregationFunctionName()

Returns the aggregation function name for representation in a generate expression string.

Returns:

aggregation function name

equalsNodeAggregateMethodOnly

protected abstract boolean equalsNodeAggregateMethodOnly(ExprAggregateNode node)

Return true if a expression aggregate node semantically equals the current node, or false if not.

For use by the equalsNode implementation which compares the distinct flag.

Parameters:

node - to compare to

Returns:

true if semantically equal, or false if not equals

validateAggregationChild

protected abstract AggregationMethodFactory validateAggregationChild(ExprValidationContext validationContext)
                                                              throws ExprValidationException

Gives the aggregation node a chance to validate the sub-expression types.

Parameters:

validationContext - validation information

Returns:

aggregation function factory to use

Throws:

ExprValidationException - when expression validation failed

getPositionalParams

public ExprNode[] getPositionalParams()

Specified by:

getPositionalParams in interface ExprAggregateNode

getExprEvaluator

public ExprEvaluator getExprEvaluator()

Specified by:

getExprEvaluator in interface ExprNode

isConstantResult

public boolean isConstantResult()

Description copied from interface: ExprNode

Returns true if the expression node's evaluation value doesn't depend on any events data, as must be determined at validation time, which is bottom-up and therefore reliably allows each node to determine constant value.

Specified by:

isConstantResult in interface ExprNode

Returns:

true for constant evaluation value, false for non-constant evaluation value

validate

public ExprNode validate(ExprValidationContext validationContext)
                  throws ExprValidationException

Specified by:

validate in interface ExprValidator

Throws:

ExprValidationException

validatePositionals

public void validatePositionals()
                         throws ExprValidationException

Specified by:

validatePositionals in interface ExprAggregateNode

Throws:

ExprValidationException

getType

public java.lang.Class getType()

Description copied from interface: ExprEvaluator

Returns the type that the node's evaluate method returns an instance of.

Specified by:

getType in interface ExprEvaluator

Returns:

type returned when evaluated

getFactory

public AggregationMethodFactory getFactory()

Returns the aggregation state factory for use in grouping aggregation states per group-by keys.

Specified by:

getFactory in interface ExprAggregateNode

Returns:

prototype aggregation state as a factory for aggregation states per group-by key value

setAggregationResultFuture

public void setAggregationResultFuture(AggregationResultFuture aggregationResultFuture,
                                       int column)

Assigns to the node the future which can be queried for the current aggregation state at evaluation time.

Specified by:

setAggregationResultFuture in interface ExprAggregateNode

Parameters:

aggregationResultFuture - - future containing state

column - - column to hand to future for easy access

evaluate

public final java.lang.Object evaluate(EventBean[] events,
                                       boolean isNewData,
                                       ExprEvaluatorContext exprEvaluatorContext)

Description copied from interface: ExprEvaluator

Evaluate event tuple and return result.

Specified by:

evaluate in interface ExprEvaluator

Parameters:

events - - event tuple

isNewData - - indicates whether we are dealing with new data (istream) or old data (rstream)

exprEvaluatorContext - context for expression evaluation

Returns:

evaluation result, a boolean value for OR/AND-type evalution nodes.

isDistinct

public boolean isDistinct()

Returns true if the aggregation node is only aggregatig distinct values, or false if aggregating all values.

Specified by:

isDistinct in interface ExprAggregateNode

Returns:

true if 'distinct' keyword was given, false if not

equalsNode

public final boolean equalsNode(ExprNode node)

Description copied from interface: ExprNode

Return true if a expression node semantically equals the current node, or false if not.

Concrete implementations should compare the type and any additional information that impact the evaluation of a node.

Specified by:

equalsNode in interface ExprNode

Parameters:

node - to compare to

Returns:

true if semantically equal, or false if not equals

validateNumericChildAllowFilter

protected final java.lang.Class validateNumericChildAllowFilter(boolean hasFilter)
                                                         throws ExprValidationException

For use by implementing classes, validates the aggregation node expecting a single numeric-type child node.

Returns:

numeric type of single child

Throws:

ExprValidationException - if the validation failed

makeExceptionExpectedParamNum

protected ExprValidationException makeExceptionExpectedParamNum(int lower,
                                                                int upper)

toPrecedenceFreeEPL

public void toPrecedenceFreeEPL(java.io.StringWriter writer)

Specified by:

toPrecedenceFreeEPL in class ExprNodeBase

getPrecedence

public ExprPrecedenceEnum getPrecedence()

Description copied from interface: ExprNode

Returns precedence.

Specified by:

getPrecedence in interface ExprNode

Returns:

precedence

validateFilter

public void validateFilter(ExprEvaluator filterEvaluator)
                    throws ExprValidationException

Throws:

ExprValidationException

getOptionalLocalGroupBy

public ExprAggregateLocalGroupByDesc getOptionalLocalGroupBy()

Specified by:

getOptionalLocalGroupBy in interface ExprAggregateNode

isExprTextWildcardWhenNoParams

protected boolean isExprTextWildcardWhenNoParams()