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:

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
 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.
 Object getCoordId(int icoord)
          Returns an identifier for one of the the columns produced by this object.
 Object 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.
 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.
 

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

Object getMaskId()
Returns an identifier for the row mask for this object.

Returns:
mask identifier, should implement equals sensibly

getCoordId

Object getCoordId(int icoord)
Returns an identifier for one of the the columns produced by this object.

Parameters:
icoord - column index
Returns:
column identifier, should implement equals sensibly

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; elements may be null if not known

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

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


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