Class Table

java.lang.Object

Table

public class Table
extends Object

A class that represents a table in a relational database.

Constructor Summary

Constructors

Constructor and Description
Table(String name) Constructs a Table object with the specified name.

Method Summary

Modifier and Type	Method and Description
void	addColumn(Column c) Adds a column to the list of columns for this table.
static void	cacheClose() Closes the in-memory cache of open tables, which closes all the BDB database handles for the open tables.
static void	cacheInit() Initializes the in-memory cache of open tables.
void	close() Closes the table and ensures all changes have been written to disk.
String	dbName() Returns the name of the table's BDB database file.
Column	getColumn(int i) Returns the column with the specified index in this table.
Database	getDB() Returns the database handle for this table's underlying database.
String	getName() Returns the name of the table.
String	getRangeVar() Returns the range variable (if any) associated with this table.
int	numColumns() Returns the number of columns in this table.
OperationStatus	open() Opens the table so that it can be accessed by SQL commands.
Column	primaryKeyColumn() Returns the column (if any) that is the primary key of this table.
void	setDB(Database db) Sets the database handle for this table's underlying database.
void	setRangeVariable(String r) Sets a range variable (i.e., an alias) for this table.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Table

public Table(String name)

Constructs a Table object with the specified name.

Parameters:

name - the name of the table

Method Detail

open

public OperationStatus open()
                     throws DatabaseException

Opens the table so that it can be accessed by SQL commands. Opens the Database handle for the underlying BDB database, and fills in the Table object with the metadata stored in the catalog for this table. IMPORTANT: this should only be used to open tables that have already been created. New tables should be opened in the code that implements the CREATE TABLE command.

Returns:

OperationStatus.NOTFOUND if the table does not exist, and OperationStatus.SUCCESS otherwise.

Throws:

DatabaseException - if Berkeley DB encounters a problem opening the underlying database.

close

public void close()
           throws DatabaseException

Closes the table and ensures all changes have been written to disk. It also removes the table from the in-memory cache of open tables. If the Table.cacheClose() method is invoked to close all tables, it is not necessary to call this method as well.

Throws:

DatabaseException - if Berkeley DB encounters a problem closing the underlying database.

primaryKeyColumn

public Column primaryKeyColumn()

Returns the column (if any) that is the primary key of this table.

Returns:

the primary key column, or null if there is no primary key

Throws:

RuntimeException - if the table object does not have any columns associated with it

dbName

public String dbName()

Returns the name of the table's BDB database file.

Returns:

the name of the database file

getName

public String getName()

Returns the name of the table.

Returns:

the table's name

getRangeVar

public String getRangeVar()

Returns the range variable (if any) associated with this table.

Returns:

the range variable

getDB

public Database getDB()

Returns the database handle for this table's underlying database.

Returns:

the database handle

getColumn

public Column getColumn(int i)

Returns the column with the specified index in this table. The leftmost column has an index of 0.

Returns:

the column

Throws:

RuntimeException - if the table object does not have any columns associated with it

IndexOutOfBoundsException - if the specified index is invalid

numColumns

public int numColumns()

Returns the number of columns in this table.

Returns:

the number of columns

toString

public String toString()

Overrides:

toString in class Object

setRangeVariable

public void setRangeVariable(String r)

Sets a range variable (i.e., an alias) for this table. Used when there is a SELECT command that uses AS to rename a table in the FROM clause.

Parameters:

r - the range variable

addColumn

public void addColumn(Column c)

Adds a column to the list of columns for this table.

Parameters:

c - the column

setDB

public void setDB(Database db)

Sets the database handle for this table's underlying database.

Parameters:

db - the database handle

cacheInit

public static void cacheInit()

Initializes the in-memory cache of open tables.

cacheClose

public static void cacheClose()
                       throws DatabaseException

Closes the in-memory cache of open tables, which closes all the BDB database handles for the open tables.

Throws:

DatabaseException - if Berkeley DB encounters a problem while closing a database handle