Virtual scalar column using TaQL. More...

#include <VirtualTaQLColumn.h>

Inheritance diagram for casa::VirtualTaQLColumn:

Public Member Functions
	VirtualTaQLColumn (const String &expr)
	Construct it with the given TaQL expression.
	VirtualTaQLColumn (const Record &spec)
	Construct it with the given specification.
virtual	~VirtualTaQLColumn ()
	Destructor is mandatory.
virtual DataManager *	clone () const
	Clone the engine object.
virtual Record	dataManagerSpec () const
	Get the data manager specification.
virtual String	dataManagerType () const
	Return the type name of the engine.
const String &	expression () const
	Return the TaQL expression used.
virtual int	dataType () const
	Functions to return column info.
virtual Bool	isWritable () const
	Test if data can be put into this column.
virtual uInt	ndim (uInt rownr)
	Get the dimensionality of the item in the given row.
virtual IPosition	shape (uInt rownr)
	Get the shape of the item in the given row.
virtual Bool	isShapeDefined (uInt rownr)
	Is the value shape defined in the given row? By default it returns True.
Static Public Member Functions
static String	className ()
	Return the name of the class.
static void	registerClass ()
	Register the class name and the static makeObject "constructor".
static DataManager *	makeObject (const String &dataManagerName, const Record &spec)
	Define the "constructor" to construct this engine when a table is read back.
Private Member Functions
	VirtualTaQLColumn (const VirtualTaQLColumn &)

VirtualTaQLColumn &	operator= (const VirtualTaQLColumn &)
	Assignment is not needed and therefore forbidden (so it is made private).
virtual DataManagerColumn *	makeScalarColumn (const String &columnName, int dataType, const String &)
	Create the column object for the scalar column in this engine.
virtual DataManagerColumn *	makeIndArrColumn (const String &columnName, int dataType, const String &dataTypeId)
	Create the column object for the indirect array column in this engine.
virtual void	create (uInt)
	Let the engine initialize the object for a new table.
virtual void	prepare ()
	Prepare compiles the expression.
virtual void	getBoolV (uInt rownr, Bool *dataPtr)
	Get the scalar value in the given row.
virtual void	getuCharV (uInt rownr, uChar *dataPtr)
virtual void	getShortV (uInt rownr, Short *dataPtr)
virtual void	getuShortV (uInt rownr, uShort *dataPtr)
virtual void	getIntV (uInt rownr, Int *dataPtr)
virtual void	getuIntV (uInt rownr, uInt *dataPtr)
virtual void	getfloatV (uInt rownr, float *dataPtr)
virtual void	getdoubleV (uInt rownr, double *dataPtr)
virtual void	getComplexV (uInt rownr, Complex *dataPtr)
virtual void	getDComplexV (uInt rownr, DComplex *dataPtr)
virtual void	getStringV (uInt rownr, String *dataPtr)
virtual void	getArrayV (uInt rownr, void *dataPtr)
	Get the array value in the given row.
IPosition	getResult (uInt rownr, void *dataPtr)
	Get the result.
void	clearCurResult ()
	Clear the result cache.
Private Attributes
int	itsDataType
Bool	itsIsArray
String	itsColumnName
String	itsExpr
TableExprNode *	itsNode
Bool	itsTempWritable
Int	itsCurRow
void *	itsCurResult
IPosition	itsCurShape

Detailed Description

Virtual scalar column using TaQL.

Review Status

Reviewed By:: GvD
Date Reviewed:: 2004/07/09

Prerequisite

VirtualScalarColumn

Synopsis

VirtualTaQLColumn is a virtual column engine to define the contents of a column as a TaQL expression in which possibly other columns are used. It is (of course) only possible to get data from the column; puts cannot be done.
The expression result can be a scalar or array of the basic TaQL data types. The column data type has to be conformant with that TaQL type, thus a column of any integer type has to be used for an integer TaQL result.
Caution: One has to be careful with deleting columns; If in an existing table a TaQL expression uses a deleted column, the expression cannot be parsed anymore and the table cannot be opened anymore; In the future the Table System will be made more forgiving;

Example

The following example creates a table with a few columns. One column is virtual and has a random value if Col3 is true. Otherwise it has value 0.

       // Create the table description.
       TableDesc td;
       td.addColumn (ScalarColumnDesc<DComplex>("Col1"));
       td.addColumn (ScalarColumnDesc<Int>("Col2"));
       td.addColumn (ScalarColumnDesc<Bool>("Col3"));
       td.addColumn (ScalarColumnDesc<Double>("ColVirt"));
     
       // Now create a new table from the description.
       SetupNewTable newTab("tmtest", td, Table::New);
       // Define the expression of the virtual column and bind the column to it.
       // The other columns are by default bound to StandardStMan.
       VirtualTaQLColumn engine("iif(Col3,rand(),0)");
       newTab.bindColumn("ColVirt", engine);
       Table tab(newTab);

Definition at line 88 of file VirtualTaQLColumn.h.

Constructor & Destructor Documentation

casa::VirtualTaQLColumn::VirtualTaQLColumn ( const String & expr )

Construct it with the given TaQL expression.

casa::VirtualTaQLColumn::VirtualTaQLColumn ( const Record & spec )

Construct it with the given specification.

virtual casa::VirtualTaQLColumn::~VirtualTaQLColumn ( ) [virtual]

Destructor is mandatory.

casa::VirtualTaQLColumn::VirtualTaQLColumn ( const VirtualTaQLColumn & ) [private]

Copy is not needed and therefore forbidden (so it is made private).

Member Function Documentation

static String casa::VirtualTaQLColumn::className ( ) [static]

Return the name of the class.

void casa::VirtualTaQLColumn::clearCurResult ( ) [private]

Clear the result cache.

virtual DataManager* casa::VirtualTaQLColumn::clone ( ) const [virtual]

Clone the engine object.

Implements casa::DataManager.

virtual void casa::VirtualTaQLColumn::create ( uInt ) [private, virtual]

Let the engine initialize the object for a new table.

It defines a column keyword holding the expression.

Reimplemented from casa::VirtualColumnEngine.

virtual Record casa::VirtualTaQLColumn::dataManagerSpec ( ) const [virtual]

Get the data manager specification.

Reimplemented from casa::DataManager.

virtual String casa::VirtualTaQLColumn::dataManagerType ( ) const [virtual]

Return the type name of the engine.

(i.e. its class name VirtualTaQLColumn).

Implements casa::DataManager.

virtual int casa::VirtualTaQLColumn::dataType ( ) const [virtual]

Functions to return column info.

Implements casa::DataManagerColumn.

const String& casa::VirtualTaQLColumn::expression ( ) const [inline]

Return the TaQL expression used.

Definition at line 128 of file VirtualTaQLColumn.h.

References itsExpr.

virtual void casa::VirtualTaQLColumn::getArrayV	(	uInt	rownr,
		void *	dataPtr
	)		`[private, virtual]`

Get the array value in the given row.

The argument dataPtr is in fact an Array<T>*, but a void* is needed to be generic. The array pointed to by dataPtr has to have the correct shape (which is guaranteed by the ArrayColumn get function). The default implementation throws an "invalid operation" exception.

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getBoolV	(	uInt	rownr,
		Bool *	dataPtr
	)		`[private, virtual]`

Get the scalar value in the given row.

The default implementation throws an "invalid operation" exception.

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getComplexV	(	uInt	rownr,
		Complex *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getDComplexV	(	uInt	rownr,
		DComplex *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getdoubleV	(	uInt	rownr,
		double *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getfloatV	(	uInt	rownr,
		float *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getIntV	(	uInt	rownr,
		Int *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

IPosition casa::VirtualTaQLColumn::getResult	(	uInt	rownr,
		void *	dataPtr
	)		`[private]`

Get the result.

virtual void casa::VirtualTaQLColumn::getShortV	(	uInt	rownr,
		Short *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getStringV	(	uInt	rownr,
		String *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getuCharV	(	uInt	rownr,
		uChar *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getuIntV	(	uInt	rownr,
		uInt *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual void casa::VirtualTaQLColumn::getuShortV	(	uInt	rownr,
		uShort *	dataPtr
	)		`[private, virtual]`

Reimplemented from casa::DataManagerColumn.

virtual Bool casa::VirtualTaQLColumn::isShapeDefined ( uInt rownr ) [virtual]

Is the value shape defined in the given row? By default it returns True.

Reimplemented from casa::DataManagerColumn.

virtual Bool casa::VirtualTaQLColumn::isWritable ( ) const [virtual]

Test if data can be put into this column.

This does not test if the data file is writable, only if it is in principle allowed to store data into the column. (It may not be allowed for virtual columns). The default is True.

Reimplemented from casa::DataManagerColumn.

virtual DataManagerColumn* casa::VirtualTaQLColumn::makeIndArrColumn	(	const String &	columnName,
		int	dataType,
		const String &	dataTypeId
	)		`[private, virtual]`

Create the column object for the indirect array column in this engine.

Reimplemented from casa::VirtualColumnEngine.

static DataManager* casa::VirtualTaQLColumn::makeObject	(	const String &	dataManagerName,
		const Record &	spec
	)		`[static]`

Define the "constructor" to construct this engine when a table is read back.

This "constructor" has to be registered by the user of the engine. If the engine is commonly used, its registration can be added into the registerAllCtor function in DataManReg.cc. This function gets automatically invoked by the table system.