uk.ac.starlink.ttools.plot2.data

Interface DataSpec

All Known Implementing Classes:

AbstractDataSpec, ColumnDataSpec, JELDataSpec

@Equality
public interface DataSpec

Defines the table-like data that is required for a certain plot. This object does not store the data itself, but can be passed to a DataStore object to obtain it. A DataSpec has a small memory footprint, is cheap to produce, and can be examined to determine what data is required.

The data specification is an aggregation of the following items:

• The table the data comes from
• A list of the columns, or column-like objects, used from the table
• An identifier for a mask indicating which rows from the table will be included

Two DataSpecs should evaluate equal if their specification of the above items have the same content, that is if they would generate the same TupleSequence when presented to a DataStore.

Since:

7 Feb 2013

Author:

Mark Taylor

Method Summary

Modifier and Type	Method and Description
UserDataReader	createUserDataReader() Returns an object that can be used to read the mask and coordinate values from a row sequence derived from this object's source table.
Coord	getCoord(int icoord) Returns the coord reader that can read the data for one of this object's output columns.
int	getCoordCount() Returns the number of columns that this object produces.
String	getCoordId(int icoord) Returns an identifier for one of the the columns produced by this object.
String	getMaskId() Returns an identifier for the row mask for this object.
StarTable	getSourceTable() Returns the table object from which this data spec's data is obtained.
ValueInfo[]	getUserCoordInfos(int icoord) Returns the metadata, if known, for the values supplied by the user to provide data for one of this object's output columns.
DomainMapper[]	getUserCoordMappers(int icoord) Returns the domain mappers to use for the values supplied by the user to provide data for one of this object's output columns.
boolean	isCoordBlank(int icoord) Indicates whether the value for a given coord specified by this object is known to have a constant, blank value in all cases.
boolean	isMaskTrue() Indicates whether the mask flag specified by this object is known always to be true.

Method Detail

getSourceTable

StarTable getSourceTable()

Returns the table object from which this data spec's data is obtained.

Returns:

data source table

getCoordCount

int getCoordCount()

Returns the number of columns that this object produces.

Returns:

TupleSequence column count

getMaskId

String getMaskId()

Returns an identifier for the row mask for this object. Masks with the same identifier must mean the same thing, and preferably vice versa.

Returns:

mask identifier

getCoordId

String getCoordId(int icoord)

Returns an identifier for one of the the columns produced by this object. Coords with the same identifier must mean the same thing, and preferably vice versa.

Parameters:

icoord - column index

Returns:

column identifier

getCoord

Coord getCoord(int icoord)

Returns the coord reader that can read the data for one of this object's output columns.

Parameters:

icoord - column index

Returns:

column data reader

getUserCoordInfos

ValueInfo[] getUserCoordInfos(int icoord)

Returns the metadata, if known, for the values supplied by the user to provide data for one of this object's output columns.

Parameters:

icoord - column index

Returns:

array of value infos for column data inputs; elements may be null if not known

getUserCoordMappers

DomainMapper[] getUserCoordMappers(int icoord)

Returns the domain mappers to use for the values supplied by the user to provide data for one of this object's output columns. These objects define how the input values as supplied by the user are to be interpreted as the expected input values for this dataspec. In many cases this mapping is trivial (for instance Y axis coordinate), but in some (for instance absolute epoch) it may not be.

Parameters:

icoord - column index

Returns:

array of DomainMappers for column data inputs

createUserDataReader

UserDataReader createUserDataReader()

Returns an object that can be used to read the mask and coordinate values from a row sequence derived from this object's source table. A given UserDataReader can only be used from a single thread, but multiple returns from this method may be used concurrently in different threads.

Returns:

new data reader

isMaskTrue

boolean isMaskTrue()

Indicates whether the mask flag specified by this object is known always to be true. If true is returned, then getUserDataReader().getMaskFlag will always return true. False negatives are permitted; even if the result is false, the mask may in fact always return true.

Returns:

true if all rows are known to be included in the mask

isCoordBlank

boolean isCoordBlank(int icoord)

Indicates whether the value for a given coord specified by this object is known to have a constant, blank value in all cases. Clients don't have to test this, since data stores will always dispense the relevant blank value based on this data spec, and should do so in an efficient manner, but it may be useful for clients to know in advance that a column is blank all the way down. False negatives are permitted: even if the result is false, the column may in fact have all blank values.

Parameters:

icoord - column index

Returns:

true if all values in the column are always blank