Class RowPermutedStarTable

java.lang.Object
uk.ac.starlink.table.WrapperStarTable
uk.ac.starlink.table.RowPermutedStarTable
All Implemented Interfaces:
Closeable, AutoCloseable, StarTable

public class RowPermutedStarTable extends WrapperStarTable
Wrapper table which provides a view of a base table in which the rows are permuted. Each row in the wrapper table is a view of one in the base table. It is permitted for the wrapper to contain multiple views of the same column in the base.

A long[] array, rowMap, is used to keep track of which rows in this table correspond to which rows in the base table; the n'th row in this table corresponds to the rowMap[n]'th row in the base table. The rowMap array may contain duplicate entries, but should not contain any entries larger than the number of rows in the base table. Any negative entry is treated as a special case resulting in a 'blank' row of all null values. It can be modified during the life of the table, but it's not a good idea to do this while a RowSequence is active.

Author:
Mark Taylor (Starlink)
  • Constructor Details

    • RowPermutedStarTable

      public RowPermutedStarTable(StarTable baseTable, long[] rowMap)
      Constructs a new RowPermutedStarTable from a base table and a rowMap array.

      baseTable must provide random access.

      Parameters:
      baseTable - base table
      rowMap - array mapping rows in the new permuted table to rows in baseTable
      Throws:
      IllegalArgumentException - if baseTable.isRandom returns false
    • RowPermutedStarTable

      public RowPermutedStarTable(StarTable baseTable)
      Constructs a new RowPermutedTable with rows initially in unpermuted order.
      Parameters:
      baseTable - base table
  • Method Details

    • getRowMap

      public long[] getRowMap()
      Returns the mapping array.
      Returns:
      array mapping rows in this table to rows in the base table
    • setRowMap

      public void setRowMap(long[] rowMap)
      Sets the mapping array.
      Parameters:
      rowMap - array mapping rows in this table to rows in the base table
    • getRowCount

      public long getRowCount()
      Description copied from interface: StarTable
      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.
      Specified by:
      getRowCount in interface StarTable
      Overrides:
      getRowCount in class WrapperStarTable
      Returns:
      the number of rows, or -1
    • isRandom

      public boolean isRandom()
      Returns true.
      Specified by:
      isRandom in interface StarTable
      Overrides:
      isRandom in class WrapperStarTable
      Returns:
      true if table random access methods are available
    • getRowAccess

      public RowAccess getRowAccess() throws IOException
      Description copied from interface: StarTable
      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.
      Specified by:
      getRowAccess in interface StarTable
      Overrides:
      getRowAccess in class WrapperStarTable
      Returns:
      new RowAccess
      Throws:
      IOException - if there is an error setting up access
    • getRowSequence

      public RowSequence getRowSequence() throws IOException
      Description copied from interface: StarTable
      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.
      Specified by:
      getRowSequence in interface StarTable
      Overrides:
      getRowSequence in class WrapperStarTable
      Returns:
      new RowSequence
      Throws:
      IOException - if there is an error providing access
    • getRowSplittable

      public RowSplittable getRowSplittable() throws IOException
      Description copied from interface: StarTable
      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).

      Specified by:
      getRowSplittable in interface StarTable
      Overrides:
      getRowSplittable in class WrapperStarTable
      Returns:
      new RowSplittable
      Throws:
      IOException
      See Also:
    • getCell

      public Object getCell(long irow, int icol) throws IOException
      Description copied from interface: StarTable
      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.

      Specified by:
      getCell in interface StarTable
      Overrides:
      getCell in class WrapperStarTable
      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
    • getRow

      public Object[] getRow(long irow) throws IOException
      Description copied from interface: StarTable
      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.

      Specified by:
      getRow in interface StarTable
      Overrides:
      getRow in class WrapperStarTable
      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