org.objectweb.cjdbc.controller.cache
Class QueryCache

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

public class QueryCache

extends AbstractRequestCache

This is a query cache implementation with tunable granularity.
Cache invalidation granularity can take on of the following values:

• NO_INVALIDATE: no invalidation, the cache is inconsistent and this should just be used to determine hit ratio upper bound.
• DATABASE: the cache is flushed each time the database is updated (every INSERT, UPDATE, DELETE, ... statement).
• TABLE: table granularity, entries in the cache are invalidated based on table dependencies.
• COLUMN: column granularity, entries in the cache are invalidated based on column dependencies
• COLUMN_UNIQUE: same as COLUMN except that UNIQUE queries that selects a single row based on a key are not invalidated on INSERT.

Version:

1.0

Author:

Emmanuel Cecchet, Julie Marguerite, Sara Bouchenak

Field Summary

private int	cacheGrain
private CacheDatabaseSchema	cdbs
private java.util.Hashtable	entriesForTransaction
private QueryCacheEntry	lruHead
private QueryCacheEntry	lruTail
private java.util.HashSet	pendingQueries
private java.util.Hashtable	queries
private CacheStatistics	stats

Fields inherited from class org.objectweb.cjdbc.controller.cache.AbstractRequestCache

logger, parsingGranularity, pendingQueryTimeout

Constructor Summary

QueryCache(int cacheGranularity)
Creates a new Cache instance.

Method Summary

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

Methods inherited from class org.objectweb.cjdbc.controller.cache.AbstractRequestCache

getPendingQueryTimeout, setParsingGranularity, setPendingQueryTimeout

Methods inherited from class java.lang.Object

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

Field Detail

queries

private java.util.Hashtable queries

pendingQueries

private java.util.HashSet pendingQueries

lruHead

private QueryCacheEntry lruHead

lruTail

private QueryCacheEntry lruTail

cdbs

private CacheDatabaseSchema cdbs

entriesForTransaction

private java.util.Hashtable entriesForTransaction

cacheGrain

private int cacheGrain

stats

private CacheStatistics stats

Constructor Detail

QueryCache

public QueryCache(int cacheGranularity)

Creates a new Cache instance.

Parameters:

cacheGranularity - an int value

Method Detail

initQueryCache

private void initQueryCache(int cacheGranularity)
                     throws CacheException

Throws:

CacheException

setDatabaseSchema

public void setDatabaseSchema(DatabaseSchema dbs)

Sets the DatabaseSchema of the current virtual database.

Overrides:

setDatabaseSchema in class AbstractRequestCache

Parameters:

dbs - a DatabaseSchema value

See Also:

CacheDatabaseSchema

mergeDatabaseSchema

public void mergeDatabaseSchema(DatabaseSchema dbs)

Merge the given DatabaseSchema with the current one.

Overrides:

mergeDatabaseSchema in class AbstractRequestCache

Parameters:

dbs - a DatabaseSchema value

See Also:

CacheDatabaseSchema

addToCache

public 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, only the result is updated.

Specified by:

addToCache in class AbstractRequestCache

Parameters:

request - the request

result - the result corresponding to the request

Throws:

CacheException - if an error occurs

getFromCache

public 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.

Specified by:

getFromCache in class AbstractRequestCache

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 void removeFromCache(SelectRequest request)
                     throws CacheException

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

Specified by:

removeFromCache in class AbstractRequestCache

Parameters:

request - a SelectRequest

Throws:

CacheException - if an error occurs

writeNotify

public void writeNotify(AbstractWriteRequest request)
                 throws CacheException

Notifies the cache that this 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.

Specified by:

writeNotify in class AbstractRequestCache

Parameters:

request - an AbstractRequest value

Throws:

CacheException - if an error occurs

flushCache

public void flushCache()

Removes all entries from the cache.

Specified by:

flushCache in class AbstractRequestCache

removeOldest

protected void removeOldest()

Removes the oldest entry from the cache.

getParsingGranularity

public int getParsingGranularity()

Gets the needed query parsing granularity.

Overrides:

getParsingGranularity in class AbstractRequestCache

Returns:

needed query parsing granularity

See Also:

AbstractRequestCache.setParsingGranularity(int)

commit

public void commit(TransactionMarkerMetaData tm)
            throws CacheException

Commit a transaction given its id.

Specified by:

commit in class AbstractRequestCache

Parameters:

tm - the transaction marker metadata

Throws:

CacheException - if an error occurs

rollback

public void rollback(TransactionMarkerMetaData tm)
              throws CacheException

Rollback a transaction given its id.

Specified by:

rollback in class AbstractRequestCache

Parameters:

tm - the transaction marker metadata

Throws:

CacheException - if an error occurs

getXmlInformation

public java.lang.String getXmlInformation()

Gets information about the request cache

Specified by:

getXmlInformation in class AbstractRequestCache

Returns:

String containing information

getInformation

public java.lang.String getInformation()

Gets information about the request cache

Specified by:

getInformation in class AbstractRequestCache

Returns:

String containing information