问题:

I'm facing performance issues executing standard spring-data-jpa findAll queries using @NamedEntityGraph

When I examine the logs, I see the following statements:

2016-10-26 09:46:25,681 DEBUG [http-nio-8080-exec-1] CriteriaQueryImpl: Rendered criteria query -> select generatedAlias0 from Patient as generatedAlias0 order by generatedAlias0.id asc 2016-10-26 09:46:25,681 DEBUG [http-nio-8080-exec-1] CriteriaQueryImpl: Rendered criteria query -> select count(generatedAlias0) from Patient as generatedAlias0 2016-10-26 09:46:25,681 DEBUG [http-nio-8080-exec-1] SQL: select count(patient0_.id) as col_0_0_ from patient patient0_ 2016-10-26 09:46:25,682 DEBUG [http-nio-8080-exec-1] Loader: Result row:  2016-10-26 09:46:25,682 DEBUG [http-nio-8080-exec-1] ConcurrentStatisticsImpl: HHH000117: HQL: select count(generatedAlias0) from Patient as generatedAlias0, time: 0ms, rows: 1 2016-10-26 09:46:25,682 DEBUG [http-nio-8080-exec-1] QueryTranslatorImpl: parse() - HQL: select generatedAlias0 from com.fluidda.broncholab.domain.Patient as generatedAlias0 order by generatedAlias0.id asc 2016-10-26 09:46:27,340 DEBUG [http-nio-8080-exec-1] QueryTranslatorImpl: --- HQL AST ---  \-[QUERY] Node: 'query'     +-[SELECT_FROM] Node: 'SELECT_FROM'     |  +-[FROM] Node: 'from'     |  |  \-[RANGE] Node: 'RANGE'     |  |     +-[DOT] Node: '.'     |  |     |  +-[DOT] Node: '.'     |  |     |  |  +-[DOT] Node: '.'     |  |     |  |  |  +-[DOT] Node: '.'     |  |     |  |  |  |  +-[IDENT] Node: 'com'     |  |     |  |  |  |  \-[IDENT] Node: 'fluidda'     |  |     |  |  |  \-[IDENT] Node: 'broncholab'     |  |     |  |  \-[IDENT] Node: 'domain'     |  |     |  \-[IDENT] Node: 'Patient'     |  |     \-[ALIAS] Node: 'generatedAlias0'     |  \-[SELECT] Node: 'select'     |     \-[IDENT] Node: 'generatedAlias0'     \-[ORDER] Node: 'order'        +-[DOT] Node: '.'        |  +-[IDENT] Node: 'generatedAlias0'        |  \-[IDENT] Node: 'id'        \-[ASCENDING] Node: 'asc'  2016-10-26 09:46:27,340 DEBUG [http-nio-8080-exec-1] ErrorCounter: throwQueryException() : no errors 2016-10-26 09:46:27,340 DEBUG [http-nio-8080-exec-1] HqlSqlBaseWalker: select << begin [level=1, statement=select] 2016-10-26 09:46:27,341 DEBUG [http-nio-8080-exec-1] FromElement: FromClause{level=1} : com.fluidda.broncholab.domain.Patient (generatedAlias0) -> patient0_

There is a big gap between 2 QueryTranslatorImpl log statements: almost 2 seconds?!

When looking in the source code, I don't see anything special (hibernate-core-4.3.11.Final)

private HqlParser parse(boolean filter) throws TokenStreamException, RecognitionException {     // Parse the query string into an HQL AST.     final HqlParser parser = HqlParser.getInstance( hql );     parser.setFilter( filter );      LOG.debugf( "parse() - HQL: %s", hql );     parser.statement();      final AST hqlAst = parser.getAST();      final NodeTraverser walker = new NodeTraverser( new JavaConstantConverter() );     walker.traverseDepthFirst( hqlAst );      showHqlAst( hqlAst );      parser.getParseErrorHandler().throwQueryException();     return parser; }

What is the problem here? It is a very basic HQL, why does it takes so long?

Is it possible to cache these HQL AST parsing?

回答1:

The HQL query plans are cached, for performance considerations. You can control the query plan cache using the following two configuration properties:

hibernate.query.plan_cache_max_size = 2048 (default value)
hibernate.query.plan_parameter_metadata_max_size = 128 (default value)

Try increasing the hibernate.query.plan_cache_max_size value to a value that's appropriate for your data access patterns.

In my book, High-Performance Java Persistence, I explained why you should configure these two values properly because otherwise parsing the HQL queries might become a performance bottleneck.

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