casacore::TableExprAggrNode Class Reference

TaQL node representing a scalar aggregate function. More...

#include <ExprAggrNode.h>

Inheritance diagram for casacore::TableExprAggrNode:

List of all members.

Public Member Functions
	TableExprAggrNode (FunctionType, NodeDataType, ValueType, const TableExprNodeSet &source)
	Constructor.
virtual void	getAggrNodes (vector< TableExprNodeRep * > &aggr)
	Get the nodes representing an aggregate function.
TableExprNodeRep *	operand ()
	Get the operand node.
virtual CountedPtr < TableExprGroupFuncBase >	makeGroupAggrFunc ()
	Create the correct aggregate function object.
virtual Bool	isLazyAggregate () const
	Is the aggregate function a lazy or an immediate one?
virtual Bool	getBool (const TableExprId &id)
	Functions to get the result of an aggregate function.
virtual Int64	getInt (const TableExprId &id)
virtual Double	getDouble (const TableExprId &id)
virtual DComplex	getDComplex (const TableExprId &id)
virtual String	getString (const TableExprId &id)
virtual MVTime	getDate (const TableExprId &id)
Static Public Member Functions
static NodeDataType	checkOperands (Block< Int > &dtypeOper, ValueType &resVT, FunctionType ftype, PtrBlock< TableExprNodeRep * > &nodes)
	Check the operands of the aggregate function and return the result's data type.
Private Member Functions
TableExprGroupFuncBase *	doMakeGroupAggrFunc ()
	Do the actual creation of the correct aggregate function object.
Private Attributes
CountedPtr < TableExprGroupFuncBase >	itsFunc

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Detailed Description

TaQL node representing a scalar aggregate function.

Intended use:

Internal

Review Status

Test programs:

tTableGram

Synopsis

A TableExprAggrNode object is a special TableExprFuncNode object. Instead of operating on a single row, it operates on a group of table rows, usually formed by means of the GROUPBY clause. It aggregates the values in the rows in the group by means of an aggregation function derived from TableExprGroupFuncBase. Several standard aggregation functions (e.g., gmean, gmin, gsum) are defined in TaQL and implemented this way.

There are two types of aggregate function implementations:

• Immediate aggregate functions calculate the results while the groups are being formed. In this way they step sequentially through the data. This is only possible for functions that do not have to keep to many data in memory.
• Lazy aggregate functions calculate the results after the groups are formed using the vector of TableExprIds they get per group. In this way only data for a single group might need to be kept in memory. It is used, for instance, to calculate the median.

Note that this class handles operands that are a scalar or array. If array, all values in the array are used as individual values. Class TableExprAggrNodeArray handles aggregate functions giving an array result (e.g., function gaggr).

It is also possible to define an aggregate function in a UDF derived from class UDFBase. Such an aggregate function is instantiated as a TableExprUDFNode(Array) object, not as TabeExprAggrNode(Array). These functions are always lazy.

Definition at line 83 of file ExprAggrNode.h.

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Constructor & Destructor Documentation

casacore::TableExprAggrNode::TableExprAggrNode	(	FunctionType	,
		NodeDataType	,
		ValueType	,
		const TableExprNodeSet &	source
	)

Constructor.

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Member Function Documentation

static NodeDataType casacore::TableExprAggrNode::checkOperands	(	Block< Int > &	dtypeOper,
		ValueType &	resVT,
		FunctionType	ftype,
		PtrBlock< TableExprNodeRep * > &	nodes
	)			[static]

Check the operands of the aggregate function and return the result's data type.

TableExprGroupFuncBase* casacore::TableExprAggrNode::doMakeGroupAggrFunc

(

)

[private]

Do the actual creation of the correct aggregate function object.

virtual void casacore::TableExprAggrNode::getAggrNodes

(

vector< TableExprNodeRep * > &

aggr

)

[virtual]

Get the nodes representing an aggregate function.

Reimplemented from casacore::TableExprNodeMulti.

virtual Bool casacore::TableExprAggrNode::getBool

(

const TableExprId &

id

)

[virtual]

Functions to get the result of an aggregate function.

Reimplemented from casacore::TableExprFuncNode.

virtual MVTime casacore::TableExprAggrNode::getDate

(

const TableExprId &

id

)

[virtual]

Reimplemented from casacore::TableExprFuncNode.

virtual DComplex casacore::TableExprAggrNode::getDComplex

(

const TableExprId &

id

)

[virtual]

Reimplemented from casacore::TableExprFuncNode.

virtual Double casacore::TableExprAggrNode::getDouble

(

const TableExprId &

id

)

[virtual]

Reimplemented from casacore::TableExprFuncNode.

virtual Int64 casacore::TableExprAggrNode::getInt

(

const TableExprId &

id

)

[virtual]

Reimplemented from casacore::TableExprFuncNode.

virtual String casacore::TableExprAggrNode::getString

(

const TableExprId &

id

)

[virtual]

Reimplemented from casacore::TableExprFuncNode.

virtual Bool casacore::TableExprAggrNode::isLazyAggregate

(

)

const [virtual]

Is the aggregate function a lazy or an immediate one?

Reimplemented from casacore::TableExprNodeRep.

virtual CountedPtr<TableExprGroupFuncBase> casacore::TableExprAggrNode::makeGroupAggrFunc

(

)

[virtual]

Create the correct aggregate function object.

It is also kept in case it is a lazy aggregate function.

Reimplemented from casacore::TableExprNodeRep.

TableExprNodeRep* casacore::TableExprAggrNode::operand

(

)

[inline]

Get the operand node.

Definition at line 100 of file ExprAggrNode.h.

References casacore::TableExprFuncNode::operands().

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Member Data Documentation

CountedPtr<TableExprGroupFuncBase> casacore::TableExprAggrNode::itsFunc [private]

Definition at line 125 of file ExprAggrNode.h.

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The documentation for this class was generated from the following file:

• casacore/tables/TaQL/ExprAggrNode.h