Class RowPermutedStarTable

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.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 Detail

      • 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:
        java.lang.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 Detail

      • 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 java.io.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:
        java.io.IOException - if there is an error setting up access
      • getRowSequence

        public RowSequence getRowSequence()
                                   throws java.io.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:
        java.io.IOException - if there is an error providing access
      • getRowSplittable

        public RowSplittable getRowSplittable()
                                       throws java.io.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:
        java.io.IOException
        See Also:
        RowRunner
      • getCell

        public java.lang.Object getCell​(long irow,
                                        int icol)
                                 throws java.io.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:
        java.io.IOException - if there is an error reading the data
      • getRow

        public java.lang.Object[] getRow​(long irow)
                                  throws java.io.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:
        java.io.IOException - if there is an error reading the data