My H2/C3PO/Hibernate setup does not seem to preserving prepared statements? - database

Question

I am finding my database is the bottleneck in my application, as part of this it looks like Prepared statements are not being reused.
For example here method I use
public static CoverImage findCoverImageBySource(Session session, String src)
{
try
{
Query q = session.createQuery("from CoverImage t1 where t1.source=:source");
q.setParameter("source", src, StandardBasicTypes.STRING);
CoverImage result = (CoverImage)q.setMaxResults(1).uniqueResult();
return result;
}
catch (Exception ex)
{
MainWindow.logger.log(Level.SEVERE, ex.getMessage(), ex);
}
return null;
}
But using Yourkit profiler it says
com.mchange.v2.c3po.impl.NewProxyPreparedStatemtn.executeQuery() Count 511
com.mchnage.v2.c3po.impl.NewProxyConnection.prepareStatement() Count 511
and I assume that the count for prepareStatement() call should be lower, ais it is looks like we create a new prepared statment every time instead of reusing.
https://docs.oracle.com/javase/7/docs/api/java/sql/Connection.html
I am using C3po connecting poolng wehich complicates things a little, but as I understand it I have it configured correctly
public static Configuration getInitializedConfiguration()
{
//See https://www.mchange.com/projects/c3p0/#hibernate-specific
Configuration config = new Configuration();
config.setProperty(Environment.DRIVER,"org.h2.Driver");
config.setProperty(Environment.URL,"jdbc:h2:"+Db.DBFOLDER+"/"+Db.DBNAME+";FILE_LOCK=SOCKET;MVCC=TRUE;DB_CLOSE_ON_EXIT=FALSE;CACHE_SIZE=50000");
config.setProperty(Environment.DIALECT,"org.hibernate.dialect.H2Dialect");
System.setProperty("h2.bindAddress", InetAddress.getLoopbackAddress().getHostAddress());
config.setProperty("hibernate.connection.username","jaikoz");
config.setProperty("hibernate.connection.password","jaikoz");
config.setProperty("hibernate.c3p0.numHelperThreads","10");
config.setProperty("hibernate.c3p0.min_size","1");
//Consider that if we have lots of busy threads waiting on next stages could we possibly have alot of active
//connections.
config.setProperty("hibernate.c3p0.max_size","200");
config.setProperty("hibernate.c3p0.max_statements","5000");
config.setProperty("hibernate.c3p0.timeout","2000");
config.setProperty("hibernate.c3p0.maxStatementsPerConnection","50");
config.setProperty("hibernate.c3p0.idle_test_period","3000");
config.setProperty("hibernate.c3p0.acquireRetryAttempts","10");
//Cancel any connection that is more than 30 minutes old.
//config.setProperty("hibernate.c3p0.unreturnedConnectionTimeout","3000");
//config.setProperty("hibernate.show_sql","true");
//config.setProperty("org.hibernate.envers.audit_strategy", "org.hibernate.envers.strategy.ValidityAuditStrategy");
//config.setProperty("hibernate.format_sql","true");
config.setProperty("hibernate.generate_statistics","true");
//config.setProperty("hibernate.cache.region.factory_class", "org.hibernate.cache.ehcache.SingletonEhCacheRegionFactory");
//config.setProperty("hibernate.cache.use_second_level_cache", "true");
//config.setProperty("hibernate.cache.use_query_cache", "true");
addEntitiesToConfig(config);
return config;
}
Using H2 1.3.172, Hibernate 4.3.11 and the corresponding c3po for that hibernate version
With reproducible test case we have
HibernateStats
HibernateStatistics.getQueryExecutionCount() 28
HibernateStatistics.getEntityInsertCount() 119
HibernateStatistics.getEntityUpdateCount() 39
HibernateStatistics.getPrepareStatementCount() 189
Profiler, method counts
GooGooStaementCache.aquireStatement() 35
GooGooStaementCache.checkInStatement() 189
GooGooStaementCache.checkOutStatement() 189
NewProxyPreparedStatement.init() 189
I don't know what I shoud be counting as creation of prepared statement rather than reusing an existing prepared statement ?
I also tried enabling c3p0 logging by adding a c3p0 logger ands making it use same log file in my LogProperties but had no effect.
String logFileName = Platform.getPlatformLogFolderInLogfileFormat() + "songkong_debug%u-%g.log";
FileHandler fe = new FileHandler(logFileName, LOG_SIZE_IN_BYTES, 10, true);
fe.setEncoding(StandardCharsets.UTF_8.name());
fe.setFormatter(new com.jthink.songkong.logging.LogFormatter());
fe.setLevel(Level.FINEST);
MainWindow.logger.addHandler(fe);
Logger c3p0Logger = Logger.getLogger("com.mchange.v2.c3p0");
c3p0Logger.setLevel(Level.FINEST);
c3p0Logger.addHandler(fe);

Answer 1

Now that I have eventually got c3p0Based logging working and I can confirm the suggestion of #Stevewaldman is correct.
If you enable
public static Logger c3p0ConnectionLogger = Logger.getLogger("com.mchange.v2.c3p0.stmt");
c3p0ConnectionLogger.setLevel(Level.FINEST);
c3p0ConnectionLogger.setUseParentHandlers(false);
Then you get log output of the form
24/08/2019 10.20.12:BST:FINEST: com.mchange.v2.c3p0.stmt.DoubleMaxStatementCache ----> CACHE HIT
24/08/2019 10.20.12:BST:FINEST: checkoutStatement: com.mchange.v2.c3p0.stmt.DoubleMaxStatementCache stats -- total size: 347; checked out: 1; num connections: 13; num keys: 347
24/08/2019 10.20.12:BST:FINEST: checkinStatement(): com.mchange.v2.c3p0.stmt.DoubleMaxStatementCache stats -- total size: 347; checked out: 0; num connections: 13; num keys: 347
making it clear when you get a cache hit. When there is no cache hit yo dont get the first line, but get the other two lines.
This is using C3p0 9.2.1