Interface StarTable

All Superinterfaces:
AutoCloseable, Closeable
All Known Implementing Classes:
AbstractStarTable, AsciiStarTable, BeanStarTable, CalcStarTable, ColumnPermutedStarTable, ColumnStarTable, ColumnStoreStarTable, ConcatStarTable, ConstantStarTable, CsvStarTable, EmptyStarTable, ExplodedStarTable, JDBCStarTable, JoinStarTable, LoopStarTable, MetaCopyStarTable, MetadataStarTable, ProgressBarStarTable, ProgressLineStarTable, RandomResultSetStarTable, RandomStarTable, RowListStarTable, RowPermutedStarTable, RowSubsetStarTable, SelectorStarTable, SequentialResultSetStarTable, StreamStarTable, WrapperStarTable

public interface StarTable extends Closeable
Defines basic table functionality. A table has a fixed number of columns, and a sequence of rows, each of which has one entry for each column. The entry in each column is of the same type (or at least a subtype of a given type) for each row; this type can be determined using the ColumnInfo objects returned by getColumnInfo(int). The first row and the first column are numbered 0.

All StarTables allow sequential access, provided by calling getRowSequence(). This may in general be called multiple times so that more than one iteration can be made through the rows of the table from start to finish. The getRowSplittable() method supports multi-threaded sequential access, and is used by RowRunner. Additionally, if the isRandom() method returns true then the random access methods getRowAccess(), getRow(long) and getCell(long, int) may be used to access table contents directly.

For random tables, the getRow and getCell methods should be thread-safe. Separate RowSequence and RowAccess objects obtained from the same table should be safely usable from different threads, but a given RowSequence/RowAccess in general will not.

In general it is preferred to use getRowAccess() than the equivalent getRow/getCell methods of the table itself, since the assumption of single-threaded use may permit more efficient implementation.

Author:
Mark Taylor (Starlink)
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Relinquishes any resources associated with this table.
    getCell(long irow, int icol)
    Returns the contents of a given table cell.
    Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls.
    int
    Returns the number of columns in this table.
    getColumnInfo(int icol)
    Returns the object describing the data in a given column.
    Returns the name of this table, if it has one.
    Returns a parameter (table-wide metadata item) of this table located by its name.
    Returns a list of table parameters, that is metadata items which pertain to the entire table.
    getRow(long irow)
    Returns the contents of a given table row.
    Returns an object which can provide random access to this table's data, if random access is implemented.
    long
    Returns the number of rows in this table, if known.
    Returns an object which can iterate over all the rows in the table sequentially.
    Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.
    Returns the URL of this table, if it has one.
    boolean
    Indicates whether random access is provided by this table.
    void
    Sets the name of this table.
    default void
    Adds the given DescribedValue to the list of parameter metadata objects associated with this table.
    void
    setURL(URL url)
    Sets the URL of this table.
  • Method Details

    • getColumnCount

      int getColumnCount()
      Returns the number of columns in this table.
      Returns:
      the number of columns
    • getRowCount

      long getRowCount()
      Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.
      Returns:
      the number of rows, or -1
    • getURL

      URL getURL()
      Returns the URL of this table, if it has one. A non-null return from this method indicates that this table is in some sense persistent.
      Returns:
      the URL of this table, or null if none is known
    • setURL

      void setURL(URL url)
      Sets the URL of this table. It ought to be possible in principle to reconstruct this table by reading the resource at url. If called, the supplied url should provide the return value for subsequent calls of getURL().
      Parameters:
      url - table URL
    • getName

      String getName()
      Returns the name of this table, if it has one. The meaning of the name is not defined, but it will typically be a short string of text indicating the identity of this table.
      Returns:
      a name for this table, or null if no suitable one exists
    • setName

      void setName(String name)
      Sets the name of this table. If called, the supplied name should provide the return value for subsequent calls of getName().
      Parameters:
      name - table name
    • getParameters

      List<DescribedValue> getParameters()
      Returns a list of table parameters, that is metadata items which pertain to the entire table.
      Returns:
      a List of DescribedValue objects constituting table-wide metadata not covered elsewhere in this interface
    • getParameterByName

      default DescribedValue getParameterByName(String parname)
      Returns a parameter (table-wide metadata item) of this table located by its name. If more than one parameter with the given name exists, an arbitrary one will be returned. If no parameter with the given name exists, null will be returned.
      Parameters:
      parname - the name of the table parameter required
    • setParameter

      default void setParameter(DescribedValue dval)
      Adds the given DescribedValue to the list of parameter metadata objects associated with this table. If an item in the parameter list with the same name as the supplied value already exists, it is removed from the list.
      Parameters:
      dval - the new parameter datum to add
    • getColumnInfo

      ColumnInfo getColumnInfo(int icol)
      Returns the object describing the data in a given column.
      Parameters:
      icol - the column for which header information is required
      Returns:
      a ValueInfo object for column icol
    • getColumnAuxDataInfos

      List<ValueInfo> getColumnAuxDataInfos()
      Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls. The idea is that the resulting list can be used to find out the kind of per-column metadata which can be expected to be found in some or all columns of this table. Each item in the returned list should have a unique name, and other characteristics which are applicable to auxData items which may be returned from any of the columns in this table.

      The order of the list may indicate some sort of natural ordering of these keys. The returned list is not guaranteed to be complete; it is legal to return an empty list if nothing is known about auxiliary metadata. The list ought not to contain duplicate elements.

      Returns:
      an unmodifiable ordered set of known metadata keys
      See Also:
    • getRowSequence

      RowSequence getRowSequence() throws IOException
      Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.
      Returns:
      new RowSequence
      Throws:
      IOException - if there is an error providing access
    • getRowAccess

      RowAccess getRowAccess() throws IOException
      Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.
      Returns:
      new RowAccess
      Throws:
      IOException - if there is an error setting up access
      UnsupportedOperationException - if isRandom returns false
    • getRowSplittable

      RowSplittable getRowSplittable() throws IOException
      Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.

      The return value must be non-null, and may provide splitting arrangements specially appropriate for the implementation. If this table 'wraps' an upstream table, it is usually best to base the implementation on calls to the the upstream getRowSplittable method, so that upstream policy about how to divide up the table is respected. However, implementations without special requirements may return Tables.getDefaultRowSplittable(this).

      Returns:
      new RowSplittable
      Throws:
      IOException
      See Also:
    • isRandom

      boolean isRandom()
      Indicates whether random access is provided by this table. Only if the result is true may the getRowAccess(), getRow(long) and getCell(long, int) methods be used.
      Returns:
      true if table random access methods are available
    • getCell

      Object getCell(long irow, int icol) throws IOException
      Returns the contents of a given table cell. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().

      This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

      Parameters:
      irow - the index of the cell's row
      icol - the index of the cell's column
      Returns:
      the contents of this cell
      Throws:
      IOException - if there is an error reading the data
      UnsupportedOperationException - if isRandom returns false
    • getRow

      Object[] getRow(long irow) throws IOException
      Returns the contents of a given table row. The returned value is equivalent to an array formed of all the objects returned by getCell(irow,icol) for all the columns icol in sequence.

      This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

      Parameters:
      irow - the index of the row to retrieve
      Returns:
      an array of the objects in each cell in row irow
      Throws:
      IOException - if there is an error reading the data
      UnsupportedOperationException - if isRandom returns false
    • close

      void close() throws IOException
      Relinquishes any resources associated with this table. This may do nothing, and calling it is often not required, but it provides an opportunity to force release of file descriptors or other resources that are not well handled by garbage collection if the table itself holds them. It is not intended for release of heap-based resources, for which garbage collection already provides adequate management.

      Following a call to this method, any attempt to use this table or objects such as RowSequences obtained from it will result in undefined behaviour.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException