ArrColDesc.h

Classes

ArrayColumnDesc -- Templated class for description of table array columns (full description)

class ArrayColumnDesc : public BaseColumnDesc

Interface

Public Members

explicit ArrayColumnDesc (const String& name, Int ndim = -1, int options = 0)

ArrayColumnDesc (const String& name, const String& comment, Int ndim = -1, int options = 0)

ArrayColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, Int ndim = -1, int options = 0)

ArrayColumnDesc (const String& name, const IPosition& shape, int options = 0)

ArrayColumnDesc (const String& name, const String& comment, const IPosition& shape, int options = 0)

ArrayColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, const IPosition& shape, int options = 0, int ndim=-1)

ArrayColumnDesc (const ArrayColumnDesc<T>&)

~ArrayColumnDesc()

ArrayColumnDesc<T>& operator= (const ArrayColumnDesc<T>&)

BaseColumnDesc* clone() const

String className() const

PlainColumn* makeColumn (ColumnSet*) const

void show (ostream& os) const

ArrayColumnDesc (SimpleOrderedMap<String, BaseColumnDesc* (*)(const String&)>&)

Protected Members

static BaseColumnDesc* makeDesc(const String& name)

virtual void putDesc (AipsIO&) const

virtual void getDesc (AipsIO&)

Description

Review Status

Reviewed By:: Gareth Hunt
Date Reviewed:: 94Nov17

Prerequisite

BaseColumnDesc (and its prerequisites)
TableDesc

Etymology

This class builds descriptions of table columns where each cell (which may also be called a row) will hold an array.

Synopsis

ArrayColumnDesc is a templated class for defining a table column containing arrays.

The table values are handled by a data manager. This can be a storage manager to store the values in a file or it can be a virtual column engine to calculate them on-the-fly. Only the basic data types are allowed when storing in a file. These are: Bool, uChar, Short, uShort, Int, uInt, float, double, Complex, DComplex and String.

At table creation time (when a table gets created from a table description), each column needs to be bound to a data manager. If not done explicitly, the table system will bind a column to the default manager defined in the column description.

An array column description consists of the following attributes:

Name, which has to be unique and must also be different from possible table keyword names.
Data type, which is determined by the template parameter (e.g. ArrayColumnDesc).
A data type id, which tells the unique name of non-standard data types (i.e. for data type == TpOther).
Comment, which defaults to the empty string. This serves purely as an informational string for the user.
Dimensionality. If given, all arrays in the column need to have that dimensionality.
Shape. If given, all arrays in the column need to have that shape.
Default data manager, which will be used if a column for a newly created table is not explicitly bound to a datamanager.
Data manager group, which serves 2 purposes. Firstly it can be used in class SetupNewTable to bind a group of columns. Secondly, when the default data managers are used, it allows, for example, to have 2 AipsIO storage managers. One for one group of columns and one for another group of columns.
Options. These are defined in ColumnDesc.h and can be combined by logically or-ing them.
1. ColumnDesc::FixedShape says that the arrays in all cells of a column have the same shape. This shape must be defined before a table is created. It does not tell if the array is direct or indirect. A FixedShape array is defined in every cell, while for non-FixedShape arrays a cell can be empty.
2. ColumnDesc::Direct determines if an array is directly stored in the table or if it is stored indirectly in a separate file. Direct arrays enforce the FixedShape option. Usually indirect arrays are only read in on command, while direct arrays are held in memory. So the size of the arrays is an important factor.
Default keyword set, which defaults to an empty set. When a table column gets created from the description, it gets a copy of this keyword set as its initial keyword set.

There are several constructors, which allow the definition of most of the above mentioned attributes. Others, like the default keyword set, have to be defined explicitly.

This class is derived from BaseColumnDesc, thus the functions in there also apply to this class.

Once a column description is set up satisfactorily, it must be added to a table description before it can be used by the table system.

Example

     TableDesc tabDesc("tTableDesc", "1", TableDesc::New);

     // Now define array columns.
     // This one is indirect and has no dimensionality mentioned yet.
     // Define the keyword UNIT in it.
     ArrayColumnDesc<Complex> arr1Column("Arr1", "comment for Arr1");
     arr1Column.rwKeywordSet().define ("UNIT", "Jy");
     tabDesc.addColumn (arr1Column);

     // This one is indirect and has 3-dim arrays.
     tabDesc.addColumn (ArrayColumnDesc<Int>("Arr2",
                                             "comment for Arr2",
                                             3));
     // This one is direct and has 2-dim arrays with axis lengths 4 and 7.
     tabDesc.addColumn (ArrayColumnDesc<uInt>("Arr3",
                                              "comment for Arr1",
        				        IPosition(2,4,7),
 					        ColumnDesc::Direct));

Motivation

Several column description classes are needed to allow the user to define attributes which are special for each column type. For scalars the special attribute is the default value. They all have to be templated to support arbitrary data types.

Template Type Argument Requirements (T)

Default constructor
Copy constructor
Assignment operator
static String dataTypeId(); // (not needed for builtin types) This should return the unique "name" of the class.

Member Description

explicit ArrayColumnDesc (const String& name, Int ndim = -1, int options = 0)

Construct the column with the given name and dimensionality. The data manager type defaults to the StandardStman storage manager. The data manager group defaults to the data manager type. Ndim <=0 means that the number of dimensions is free and will be defined when creating the table (rows). Ndim>0 means that the arrays in this column must have the given dimensionality. The possible options are defined in ColumnDesc.h.

ArrayColumnDesc (const String& name, const String& comment, Int ndim = -1, int options = 0)

Construct the column with the given name, dimensionality, and comment. The data manager type defaults to the StandardStman storage manager. The data manager group defaults to the data manager type. Ndim <=0 means that the number of dimensions is free and will be defined when creating the table (rows). Ndim>0 means that the arrays in this column must have the given dimensionality. The possible options are defined in ColumnDesc.h.

ArrayColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, Int ndim = -1, int options = 0)

Construct the column with the given name, dimensionality, comment, and default data manager type and group. A blank data manager group defaults to the data manager type. Ndim <=0 means that the number of dimensions is free and will be defined when creating the table (rows). Ndim>0 means that the arrays in this column must have the given dimensionality. The possible options are defined in ColumnDesc.h.

ArrayColumnDesc (const String& name, const IPosition& shape, int options = 0)

Construct the column with the given name and shape. The data manager type defaults to the StandardStman storage manager. The data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h. This constructor can only be used for FixedShape arrays, because the shape of other arrays can only be set per row.

ArrayColumnDesc (const String& name, const String& comment, const IPosition& shape, int options = 0)

Construct the column with the given name, shape, and comment. The data manager type defaults to the StandardStman storage manager. The data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h. This constructor can only be used for FixedShape arrays, because the shape of other arrays can only be set per row.

ArrayColumnDesc (const String& name, const String& comment, const String& dataManName, const String& dataManGroup, const IPosition& shape, int options = 0, int ndim=-1)

Construct the column with the given name, shape, comment, and default data manager type and group. A blank data manager group defaults to the data manager type. The possible options are defined in ColumnDesc.h. This constructor can only be used for FixedShape arrays, because the shape of other arrays can only be set per row. If both ndim and shape are given as > 0, ndim should match the length of shape.