Class to hold table lock options. More...

#include <TableLock.h>

Inheritance diagram for casa::TableLock:

Public Types
enum	LockOption { PermanentLocking, PermanentLockingWait, AutoLocking, UserLocking, AutoNoReadLocking, UserNoReadLocking, DefaultLocking }
	Define the possible table locking options. More...
Public Member Functions
	TableLock (LockOption option=DefaultLocking)
	Construct with given option and interval.
	TableLock (LockOption option, double inspectionInterval, uInt maxWait=0)
	TableLock (const TableLock &that)
	Copy constructor.
TableLock &	operator= (const TableLock &that)
	Assignment.
void	merge (const TableLock &that)
	Merge that TableLock with this TableLock object by taking the maximum option and minimum inspection interval.
LockOption	option () const
	Get the locking option.
Bool	readLocking () const
	Is read locking needed?
Bool	isPermanent () const
	Is permanent locking used?
double	interval () const
	Get the inspection interval.
uInt	maxWait () const
	Get the maximum wait period in AutoLocking mode.
Private Member Functions
void	init ()
	Set itsOption and itsReadLocking when needed.
Private Attributes
LockOption	itsOption
Bool	itsReadLocking
uInt	itsMaxWait
double	itsInterval
Bool	itsIsDefaultLocking
Bool	itsIsDefaultInterval

Detailed Description

Class to hold table lock options.

Intended use:

Internal

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25
Test programs:: tTable

Prerequisite

class Table
class LockFile

Synopsis

This class keeps the Table lock options. Currently these are the LockingOption and the inspection interval.

It also keeps the LockFile object used to do the actual locking/unlocking.

Motivation

Encapsulate Table locking info.

Definition at line 65 of file TableLock.h.

Member Enumeration Documentation

enum casa::TableLock::LockOption

Define the possible table locking options.

They offer the user the possibility to lock and synchronize access to the table. A lot of locking degrades table performance; not only because acquiring/releasing locks takes time, but especially because table data has to be synchronized (thus written to disk) when a lock is released. Otherwise the other processes see data which is not up-to-date.

Enumerator:

PermanentLocking	The table is permanently locked. A lock is set at the beginning and only released when the table is closed. A read lock is used when the table is opened for readonly; otherwise a write lock is used. This means that multiple readers are possible. The Table constructor exits with an exception when the lock cannot be acquired.
PermanentLockingWait	The same as above, but the table constructor waits until the lock gets available.
AutoLocking	The system takes care of acquiring/releasing locks. In principle it keeps the table locked, but from time to time (defined by the inspection interval) it is checked whether another process wants to access the table. If so, the lock is released and probably re-acquired later. This mode is the default mode.
UserLocking	The user is taking care of locking the table by means of the Table functions `lock` and `unlock`. In this way transaction processing can be implemented.
AutoNoReadLocking	The system takes care of acquiring/releasing locks. It is similar to AutoLocking, but no locks are needed for reading.
UserNoReadLocking	The user is taking care of locking the table by means of the Table functions `lock` and `unlock`. It is similar to UserLocking, but no locks are needed for reading.
DefaultLocking	This is the default locking option. It means that AutoLocking will be used if the table is not opened yet. Otherwise the locking options of the PlainTable objec already in use will be used.

Definition at line 75 of file TableLock.h.

Constructor & Destructor Documentation

casa::TableLock::TableLock ( LockOption option = DefaultLocking )

Construct with given option and interval.

The default LockOption is AutoLocking. In case of AutloLocking the inspection interval defines how often the table system checks if another process needs a lock on the table. It defaults to 5 seconds. The maxWait defines the maximum number of seconds the table system waits when acquiring a lock in AutoLocking mode. The default is 0 seconds meaning indefinitely.

casa::TableLock::TableLock	(	LockOption	option,
		double	inspectionInterval,
		uInt	maxWait = `0`
	)

casa::TableLock::TableLock ( const TableLock & that )

Copy constructor.

Member Function Documentation

void casa::TableLock::init ( ) [private]

Set itsOption and itsReadLocking when needed.

double casa::TableLock::interval ( ) const [inline]

Get the inspection interval.

Definition at line 188 of file TableLock.h.

References itsInterval.

Bool casa::TableLock::isPermanent ( ) const [inline]

Is permanent locking used?

Definition at line 182 of file TableLock.h.

References itsOption, PermanentLocking, and PermanentLockingWait.

uInt casa::TableLock::maxWait ( ) const [inline]

Get the maximum wait period in AutoLocking mode.

Definition at line 193 of file TableLock.h.

References itsMaxWait.

void casa::TableLock::merge ( const TableLock & that )

Merge that TableLock with this TableLock object by taking the maximum option and minimum inspection interval.

The option order (ascending) is UserLocking, AutoLocking, PermanentLocking. When an interval was defaulted, it is not taken into account. An option DefaultLocking is not taken into account.

TableLock& casa::TableLock::operator= ( const TableLock & that )

Assignment.

TableLock::LockOption casa::TableLock::option ( ) const [inline]

Get the locking option.

Definition at line 172 of file TableLock.h.

References itsOption.

Referenced by casa::TableLockData::autoRelease().

Bool casa::TableLock::readLocking ( ) const [inline]

Is read locking needed?

Definition at line 177 of file TableLock.h.

References itsReadLocking.

Referenced by casa::ColumnSet::checkReadLock().