com.mckoi.database
Class SubsetColumnTable

java.lang.Object
  com.mckoi.database.Table
      com.mckoi.database.FilterTable
          com.mckoi.database.SubsetColumnTable

All Implemented Interfaces:

RootTable, TableDataSource

public final class SubsetColumnTable
extends FilterTable
implements RootTable

This object is a filter that sits atop a Table object. Its purpose is to only provide a view of the columns that are required. In a Select query we may create a query with only the subset of columns that were originally in the table set. This object allows us to provide an interface to only the columns that the Table is allowed to access.

This method implements RootTable which means a union operation will not decend further past this table when searching for the roots.

Author:

Tobias Downer

Field Summary

Fields inherited from class com.mckoi.database.FilterTable

parent

Fields inherited from class com.mckoi.database.Table

DEBUG_QUERY

Constructor Summary

SubsetColumnTable(Table parent)
The Constructor.

Method Summary

int	findFieldName(Variable v) Given a fully qualified variable field name, ie.
TObject	getCellContents(int column, int row) Returns an object that represents the information in the given cell in the table.
int	getColumnCount() Returns the number of columns in the table.
DataTableDef	getDataTableDef() Returns the DataTableDef object that describes the columns and name of this table.
Variable	getResolvedVariable(int column) Returns a fully qualified Variable object that represents the name of the column at the given index.
void	setColumnMap(int[] mapping, Variable[] aliases) Adds a column map into this table.
java.lang.String	toString() Returns a string that represents this table.
boolean	typeEquals(RootTable table) This function is used to check that two tables are identical.

Methods inherited from class com.mckoi.database.FilterTable

getDatabase, getParent, getRowCount, hasRootsLocked, lockRoot, printGraph, rowEnumeration, unlockRoot

Methods inherited from class com.mckoi.database.Table

all, allColumnMatchesValue, any, columnContainsCell, columnContainsValue, columnMatchesValue, columnMerge, compareCells, Debug, distinct, distinct, dumpTo, emptySelect, exhaustiveSelect, fastFindFieldName, getColumnDefAt, getColumnScheme, getFirstCellContent, getFirstCellContent, getLastCellContent, getLastCellContent, getSingleCellContent, getSingleCellContent, getSystem, getTableAccessState, getTTypeForColumn, getTTypeForColumn, join, orderByColumn, orderByColumn, orderByColumn, orderByColumns, orderedRowList, outside, rangeSelect, selectAll, selectAll, selectFirst, selectLast, selectRange, selectRest, simpleJoin, simpleSelect, singleRowSelect, toMap, union

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SubsetColumnTable

public SubsetColumnTable(Table parent)

The Constructor.

Method Detail

setColumnMap

public void setColumnMap(int[] mapping,
                         Variable[] aliases)

Adds a column map into this table. The int array contains a map to the column in the parent object that we want the column number to reference. For example, to select columns 4, 8, 1, 2 into this new table, the array would be { 4, 8, 1, 2 }.

getColumnCount

public int getColumnCount()

Returns the number of columns in the table.

Overrides:

getColumnCount in class FilterTable

findFieldName

public int findFieldName(Variable v)

Given a fully qualified variable field name, ie. 'APP.CUSTOMER.CUSTOMERID' this will return the column number the field is at. Returns -1 if the field does not exist in the table.

Overrides:

findFieldName in class FilterTable

getDataTableDef

public DataTableDef getDataTableDef()

Returns the DataTableDef object that describes the columns and name of this table. For a SubsetColumnTable object, this returns the columns that were mapped via the 'setColumnMap' method.

Specified by:

getDataTableDef in interface TableDataSource

Overrides:

getDataTableDef in class FilterTable

getResolvedVariable

public Variable getResolvedVariable(int column)

Returns a fully qualified Variable object that represents the name of the column at the given index. For example, new Variable(new TableName("APP", "CUSTOMER"), "ID")

Overrides:

getResolvedVariable in class FilterTable

getCellContents

public final TObject getCellContents(int column,
                                     int row)

Returns an object that represents the information in the given cell in the table. This will generally be an expensive algorithm, so calls to it should be kept to a minimum. Note that the offset between two rows is not necessarily 1.

Specified by:

getCellContents in interface TableDataSource

Overrides:

getCellContents in class FilterTable

typeEquals

public boolean typeEquals(RootTable table)

This function is used to check that two tables are identical. This is used in operations like 'union' that need to determine that the roots are infact of the same type.

Specified by:

typeEquals in interface RootTable

toString

public java.lang.String toString()

Returns a string that represents this table.

Overrides:

toString in class Table