org.objectweb.cjdbc.controller.cache
Class AbstractRequestCache

java.lang.Object
  org.objectweb.cjdbc.controller.cache.AbstractRequestCache

Direct Known Subclasses:

QueryCache, QueryCacheDB

public abstract class AbstractRequestCache

extends java.lang.Object

This class defines the minimal functionnalities that a request cache must provide.

Only read requests (SELECTs) can be cached, there is no sense to cache writes as they do not provide any result to cache. However, the cache must be notified of the write queries in order to maintain cache coherency.

Version:

1.0

Author:

Emmanuel Cecchet

Field Summary

(package private) static Trace	logger Logger instance.
protected int	parsingGranularity Parsing granularity.
protected long	pendingQueryTimeout Pending query timeout.

Constructor Summary

AbstractRequestCache()

Method Summary

abstract void	addToCache(SelectRequest request, java.sql.ResultSet result) Adds an entry request/reply to the cache.
abstract void	commit(TransactionMarkerMetaData tm) Commit a transaction given its id.
abstract void	flushCache() Removes all entries from the cache.
abstract QueryCacheEntry	getFromCache(SelectRequest request, boolean addToPendingQueries) Gets the result to the given request from the cache.
abstract java.lang.String	getInformation() Gets information about the request cache.
int	getParsingGranularity() Gets the needed query parsing granularity.
int	getPendingQueryTimeout() Returns the pending query timeout.
abstract java.lang.String	getXmlInformation() Gets information about the request cache in xml
void	mergeDatabaseSchema(DatabaseSchema dbs) Merge the given DatabaseSchema with the current one.
abstract void	removeFromCache(SelectRequest request) Removes an entry from the cache (both request and reply are dropped).
abstract void	rollback(TransactionMarkerMetaData tm) Rollback a transaction given its id.
void	setDatabaseSchema(DatabaseSchema dbs) Sets the DatabaseSchema of the current virtual database.
void	setParsingGranularity(int parsingGranularity) Sets the needed query parsing granularity.
void	setPendingQueryTimeout(int pendingQueryTimeout) Sets the pending query timeout.
abstract void	writeNotify(AbstractWriteRequest request) Notifies the cache that the given write request has been issued, so that cache coherency can be maintained.

Methods inherited from class java.lang.Object

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

Field Detail

parsingGranularity

protected int parsingGranularity

Parsing granularity. Default is: ParsingGranularities.NO_PARSING.

pendingQueryTimeout

protected long pendingQueryTimeout

Pending query timeout. Default is: 0 (wait forever).

logger

static Trace logger

Logger instance.

Constructor Detail

AbstractRequestCache

public AbstractRequestCache()

Method Detail

getParsingGranularity

public int getParsingGranularity()

Gets the needed query parsing granularity.

Returns:

needed query parsing granularity

See Also:

setParsingGranularity(int)

setParsingGranularity

public void setParsingGranularity(int parsingGranularity)

Sets the needed query parsing granularity.

Parameters:

parsingGranularity - the query parsing granularity to set

See Also:

getParsingGranularity()

getPendingQueryTimeout

public int getPendingQueryTimeout()

Returns the pending query timeout.

Returns:

the pending query timeout.

See Also:

setPendingQueryTimeout(int)

setPendingQueryTimeout

public void setPendingQueryTimeout(int pendingQueryTimeout)

Sets the pending query timeout.

Parameters:

pendingQueryTimeout - the pending query timeout to set.

See Also:

getPendingQueryTimeout()

setDatabaseSchema

public void setDatabaseSchema(DatabaseSchema dbs)

Sets the DatabaseSchema of the current virtual database.

Parameters:

dbs - a DatabaseSchema value

See Also:

CacheDatabaseSchema

mergeDatabaseSchema

public void mergeDatabaseSchema(DatabaseSchema dbs)

Merge the given DatabaseSchema with the current one.

Parameters:

dbs - a DatabaseSchema value

See Also:

CacheDatabaseSchema

addToCache

public abstract void addToCache(SelectRequest request,
                                java.sql.ResultSet result)
                         throws CacheException

Adds an entry request/reply to the cache. Note that if the request was already in the cache, its result must be updated in any case but the request must never appear twice in the cache.

Parameters:

request - the request

result - the result corresponding to the request

Throws:

CacheException - if an error occurs

getFromCache

public abstract QueryCacheEntry getFromCache(SelectRequest request,
                                             boolean addToPendingQueries)

Gets the result to the given request from the cache.

The returned QueryCacheEntry is null if the request is not present in the cache.

An invalid QueryCacheEntry may be returned (it means that the result is null) but the already parsed query can be retrieved from the cache entry.

Parameters:

request - an SQL select request

addToPendingQueries - true if the request must be added to the pending query list on a cache miss

Returns:

the QueryCacheEntry if found, else null

removeFromCache

public abstract void removeFromCache(SelectRequest request)
                              throws CacheException

Removes an entry from the cache (both request and reply are dropped). The query is also removed from the pending query list.

Parameters:

request - a SelectRequest

Throws:

CacheException - if an error occurs

writeNotify

public abstract void writeNotify(AbstractWriteRequest request)
                          throws CacheException

Notifies the cache that the given write request has been issued, so that cache coherency can be maintained. If the cache is distributed, this method is reponsible for broadcasting this information to other caches.

Parameters:

request - an AbstractWriteRequest value

Throws:

CacheException - if an error occurs

flushCache

public abstract void flushCache()

Removes all entries from the cache.

commit

public abstract void commit(TransactionMarkerMetaData tm)
                     throws CacheException

Commit a transaction given its id.

Parameters:

tm - the transaction marker metadata

Throws:

CacheException - if an error occurs

rollback

public abstract void rollback(TransactionMarkerMetaData tm)
                       throws CacheException

Rollback a transaction given its id.

Parameters:

tm - the transaction marker metadata

Throws:

CacheException - if an error occurs

getInformation

public abstract java.lang.String getInformation()

Gets information about the request cache.

Returns:

String containing information

getXmlInformation

public abstract java.lang.String getXmlInformation()

Gets information about the request cache in xml

Returns:

xml formatted String containing information