The standard way of accessing table columns is through Strings. Mistakes in typing the column name will not be caught at compile time (and may not be caught at run time). We have therefore decided to use an enumeration to specify columns so that many mistakes will be caught at compile time. This requires functions to map to and from this enumeration to the strings that are ultimately used.
Upon destruction, the table is checked to see that the MeasurementSet remains valid, i.e., all required columns are present An exception is thrown if not all required columns are present Nevertheless, the table will be flushed to disk if it is writable - preserving its state.
A MeasurementSet has a number of required subtables. These are stored as keywords in the Table. Access to these subtables is provided via member functions (e.g. antenna() for the ANTENNA table). All subtables have associated MeasurementSet-like classes defined for them (MSAntenna for the ANTENNA table) which provide analogous column and keyword mapping as provided here.
While the class name, MeasurementSet, is descriptive, it is often too long for many common uses. The typedef MS is provided as a convenient shorthand for MeasurementSet. The example below uses this typedef.
Due to the inheritance scheme, it was necessary to separate the enumerations used by MeasurementSet into a separate class, MSMainEnums.
// create the table descriptor
TableDesc simpleDesc = MS::requiredTableDesc()
// set up a new table
SetupNewTable newTab("simpleTab", simpleDesc, Table::New);
// create the MeasurementSet
MeasurementSet simpleMS(newTab);
// now we need to define all required subtables
// the following call does this for us if we don't need to
// specify details of Storage Managers for columns.
simpleMS.createDefaultSubtables(Table::New);
// fill MeasurementSet via its Table interface
// For example, construct one of the columns
TableColumn feed(simpleMS, MS::columnName(MS::FEED1));
uInt rownr = 0;
// add a row
simpleMS.addRow();
// set the values in that row, e.g. the feed column
feed.putScalar(rownr,1);
// Access a subtable
ArrayColumn<Double> antpos(simpleMS.antenna(),
MSAntenna::columnName(MSAntenna::POSITION));
simpleMS.antenna().addRow();
Array<Double> position(3);
position(0)=1.; position(1)=2.; position(2)=3.;
antpos.put(0,position);
// etc.
There are a number of reasons why MeasurementSet is more than just a Table.
These constructors mirror the Table ones with additional checking on validity (verifying that the MS will have the required columns and keywords) An exception is thrown if the constructed Table is not a valid MS
As with tables, the destructor writes the table if necessary. Additional checking is done here to verify that all required columns are still present. If it is NOT valid, it will write the table and then throw an exception.
Assignment operator, reference semantics
Make a special copy of this MS which references all columns from this MS except those mentioned; those are empty and writable. Each forwarded column has the same writable status as the underlying column. The mentioned columns all use the AipsIO storage manager. The main use of this is for the synthesis package where corrected and model visibilities are stored as new DATA columns in an MS which references the raw MS for the other columns. Except for these special cases, the use of this function will be rare.
Return the name of each of the subtables. This should be used by the filler to create the subtables in the correct location.
Access functions for the subtables, using the MS-like interface for each
Initialize the references to the subtables. You need to call this only if you assign new subtables to the table keywords. This also checks for validity of the table and its subtables. Set clear to True to clear the subtable references (used in assignment)
Create default subtables: fills the required subtable keywords with tables of the correct type, mainly for testing and as an example of how to do this for specific fillers. In practice these tables will often have more things specified, like dimensions of arrays and storage managers for the various columns.
Initialize the statics appropriately. This does not need to be called by users, it is called by the implementation class MSTableImpl.
Create DATA column from existing FLOAT_DATA column. Noop if DATA already exists or neither exists (returns False in that case).
Validate Measure references - check that all Measure columns have their reference value set, report the ones that don't.
Flush all the tables and subtables associated with this MeasurementSet. This function calls the Table::flush() function on the main table and all the standard subtables including optional subtables. See the Table class for a description of the sync argument.
check that the MS is the latest version (2.0)