Class VirtualTable

All Implemented Interfaces:
TableDataSource

public class VirtualTable extends JoinedTable
A VirtualTable is a representation of a table whose rows are actually physically stored in another table. In other words, this table just stores pointers to rows in other tables.

We use the VirtualTable to represent temporary tables created from select, join, etc operations.

An important note about VirtualTables: When we perform a 'select' operation on a virtual table, unlike a DataTable that permanently stores information about column cell relations, we must resolve column relations between the sub-set at select time. This involves asking the tables parent(s) for a scheme to describe relations in a sub-set.

Author:
Tobias Downer
  • Field Details

    • row_list

      protected IntegerVector[] row_list
      Array of IntegerVectors that represent the rows taken from the given parents.
  • Constructor Details

    • VirtualTable

      protected VirtualTable()
  • Method Details

    • init

      protected void init(Table[] tables)
      Helper function for the constructor.
      Overrides:
      init in class JoinedTable
    • getReferenceRows

      protected IntegerVector[] getReferenceRows()
      Returns the list of IntegerVector that represents the rows that this VirtualTable references.
    • getRowCount

      public int getRowCount()
      Returns the number of rows stored in the table.
      Specified by:
      getRowCount in interface TableDataSource
      Specified by:
      getRowCount in class Table
    • resolveRowForTableAt

      protected int resolveRowForTableAt(int row_number, int table_num)
      Description copied from class: JoinedTable
      Given a row and a table index (to a parent reference table), this will return the row index in the given parent table for the given row.
      Specified by:
      resolveRowForTableAt in class JoinedTable
    • resolveAllRowsForTableAt

      protected void resolveAllRowsForTableAt(IntegerVector row_set, int table_num)
      Description copied from class: JoinedTable
      Given an IntegerVector that represents a list of pointers to rows in this table, this resolves the rows to row indexes in the given parent table. This method changes the 'row_set' IntegerVector object.
      Specified by:
      resolveAllRowsForTableAt in class JoinedTable