Package com.mckoi.database

Class FunctionTable

java.lang.Object

com.mckoi.database.Table

com.mckoi.database.AbstractDataTable

com.mckoi.database.DefaultDataTable

com.mckoi.database.FunctionTable

All Implemented Interfaces:

RootTable, TableDataSource

public class FunctionTable
extends DefaultDataTable

A table that has a number of columns and as many rows as the refering table. Tables of this type are used to construct aggregate and function columns based on an expression. They are joined with the result table in the last part of the query processing.

For example, a query like 'select id, id * 2, 8 * 9 from Part' the columns 'id * 2' and '8 * 9' would be formed from this table.

SYNCHRONIZATION ISSUE: Instances of this object are NOT thread safe. The reason it's not is because if 'getCellContents' is used concurrently it's possible for the same value to be added into the cache causing an error. It is not expected that this object will be shared between threads.

Author:

Tobias Downer

Field Summary

Fields inherited from class com.mckoi.database.DefaultDataTable

row_count

Fields inherited from class com.mckoi.database.Table

DEBUG_QUERY

Constructor Summary

Constructors

Constructor	Description
FunctionTable(Expression[] exp_list, java.lang.String[] col_names, DatabaseQueryContext context)
FunctionTable(Table cross_ref_table, Expression[] in_exp_list, java.lang.String[] col_names, DatabaseQueryContext context)	Constructs the FunctionTable.

Method Summary

Modifier and Type	Method	Description
void	createGroupMatrix(Variable[] col_list)	Creates a grouping matrix for the given tables.
TObject	getCellContents(int column, int row)	Returns an object that represents the information in the given cell in the table.
DataTableDef	getDataTableDef()	Returns the DataTableDef object that represents the columns in this function table.
Table	getReferenceTable()	Returns the Table this function is based on.
IntegerVector	groupRows(int group_number)	Returns an IntegerVector that represents the list of all rows in the group the index is at.
int	groupSize(int group_number)	The size of the group with the given number.
boolean	hasRootsLocked()	Returns true if the table has its row roots locked (via the lockRoot(int) method.
void	lockRoot(int lock_key)	Locks the root table(s) of this table so that it is impossible to overwrite the underlying rows that may appear in this table.
Table	mergeWithReference(Variable max_column)	Returns a Table that is this function table merged with the cross reference table.
static Table	resultTable(DatabaseQueryContext context, int result_val)	Returns a FunctionTable that has an int value made into a BigDecimal.
static Table	resultTable(DatabaseQueryContext context, Expression expression)	Returns a FunctionTable that has a single Expression evaluated in it.
static Table	resultTable(DatabaseQueryContext context, TObject ob)	Returns a FunctionTable that has a single TObject in it.
static Table	resultTable(DatabaseQueryContext context, java.lang.Object ob)	Returns a FunctionTable that has a single Object in it.
RowEnumeration	rowEnumeration()	Returns an Enumeration of the rows in this table.
int	rowGroup(int row_index)	Returns the group of the row at the given index.
void	setWholeTableAsGroup()	Sets the whole reference table as a single group.
void	unlockRoot(int lock_key)	Unlocks the root tables so that the underlying rows may once again be used if they are not locked and have been removed.

Methods inherited from class com.mckoi.database.DefaultDataTable

blankSelectableSchemes, blankSelectableSchemes, clearColumnScheme, findFieldName, getColumnCount, getDatabase, getResolvedVariable, getRootColumnScheme, getRowCount

Methods inherited from class com.mckoi.database.AbstractDataTable

getTableName, toString, typeEquals

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, printGraph, 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

FunctionTable

public FunctionTable(Table cross_ref_table,
                     Expression[] in_exp_list,
                     java.lang.String[] col_names,
                     DatabaseQueryContext context)

Constructs the FunctionTable.

FunctionTable

public FunctionTable(Expression[] exp_list,
                     java.lang.String[] col_names,
                     DatabaseQueryContext context)

Method Detail

setWholeTableAsGroup

public void setWholeTableAsGroup()

Sets the whole reference table as a single group.

createGroupMatrix

public void createGroupMatrix(Variable[] col_list)

Creates a grouping matrix for the given tables. The grouping matrix is arranged so that each row of the referring table that is in the group is given a number that refers to the top group entry in the group list. The group list is a linked integer list that chains through each row item in the list.

getReferenceTable

public Table getReferenceTable()

Returns the Table this function is based on. We need to provide this method for aggregate functions.

rowGroup

public int rowGroup(int row_index)

Returns the group of the row at the given index.

groupSize

public int groupSize(int group_number)

The size of the group with the given number.

groupRows

public IntegerVector groupRows(int group_number)

Returns an IntegerVector that represents the list of all rows in the group the index is at.

mergeWithReference

public Table mergeWithReference(Variable max_column)

Returns a Table that is this function table merged with the cross reference table. The result table includes only one row from each group.

The 'max_column' argument is optional (can be null). If it's set to a column in the reference table, then the row with the max value from the group is used as the group row. For example, 'Part.id' will return the row with the maximum part.id from each group.

getDataTableDef

public DataTableDef getDataTableDef()

Returns the DataTableDef object that represents the columns in this function table.

Specified by:

getDataTableDef in interface TableDataSource

Specified by:

getDataTableDef in class Table

getCellContents

public TObject getCellContents(int column,
                               int row)

Returns an object that represents the information in the given cell in the table. This can be used to obtain information about the given table cells.

Specified by:

getCellContents in interface TableDataSource

Specified by:

getCellContents in class Table

rowEnumeration

public RowEnumeration rowEnumeration()

Returns an Enumeration of the rows in this table. Each call to 'nextRowIndex' returns the next valid row index in the table.

Specified by:

rowEnumeration in interface TableDataSource

Specified by:

rowEnumeration in class Table

lockRoot

public void lockRoot(int lock_key)

Locks the root table(s) of this table so that it is impossible to overwrite the underlying rows that may appear in this table. This is used when cells in the table need to be accessed 'outside' the lock. So we may have late access to cells in the table. 'lock_key' is a given key that will also unlock the root table(s). NOTE: This is nothing to do with the 'LockingMechanism' object.

Specified by:

lockRoot in class Table

unlockRoot

public void unlockRoot(int lock_key)

Unlocks the root tables so that the underlying rows may once again be used if they are not locked and have been removed. This should be called some time after the rows have been locked.

Specified by:

unlockRoot in class Table

hasRootsLocked

public boolean hasRootsLocked()

Returns true if the table has its row roots locked (via the lockRoot(int) method.

Specified by:

hasRootsLocked in class Table

resultTable

public static Table resultTable(DatabaseQueryContext context,
                                Expression expression)

Returns a FunctionTable that has a single Expression evaluated in it. The column name is 'result'.

resultTable

public static Table resultTable(DatabaseQueryContext context,
                                TObject ob)

Returns a FunctionTable that has a single TObject in it. The column title is 'result'.

resultTable

public static Table resultTable(DatabaseQueryContext context,
                                java.lang.Object ob)

Returns a FunctionTable that has a single Object in it. The column title is 'result'.

resultTable

public static Table resultTable(DatabaseQueryContext context,
                                int result_val)

Returns a FunctionTable that has an int value made into a BigDecimal. The column title is 'result'.