Почему hibernate hql отличается причиной того, что sql отличается от левого соединения?

Ответ 1

Познакомьтесь с оператором sql, который генерирует hibernate - да, он использует ключевое слово "different", но не так, как я думаю, вы его ожидаете (или то, как подразумевается Hibernate FAQ), то есть возвращать набор "отдельных" или "уникальных" заказов.

Он не использует отдельное ключевое слово для возврата отдельных заказов, поскольку это не имеет смысла в этом SQL-запросе, учитывая указанное вами соединение.

Результирующий sql-набор по-прежнему нуждается в обработке с помощью ResultTransformer, так как явно набор sql содержит повторяющиеся заказы. Вот почему они говорят, что ключевое слово HQL не напрямую сопоставляется с ключевым словом SQL.

Ответ 2

У меня была такая же проблема, и я думаю, что это проблема спящего режима (не ошибка, потому что код не подводит). Тем не менее, я должен копать глубже, чтобы убедиться, что это проблема.

Hibernate (по крайней мере, в версии 4, версия которой я работаю над моим проектом, в частности, 4.3.11) использует концепцию SPI, длинный рассказ: как API, расширяющий или изменяющий структуру.

Я воспользовался этой возможностью, чтобы заменить классы org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory (этот класс вызывается Hibernate и делегирует задание генерации SQL-запроса) и org.hibernate.hql.internal.ast.QueryTranslatorImpl (Это своего рода внутренний класс, который вызывается org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory и генерирует фактический SQL-запрос). Я сделал это следующим образом:

Замена для org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory:

package org.hibernate.hql.internal.ast;

import java.util.Map;
import org.hibernate.engine.query.spi.EntityGraphQueryHint;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.hql.spi.QueryTranslator;

public class NoDistinctInSQLASTQueryTranslatorFactory extends ASTQueryTranslatorFactory {

    @Override
    public QueryTranslator createQueryTranslator(String queryIdentifier, String queryString, Map filters, SessionFactoryImplementor factory, EntityGraphQueryHint entityGraphQueryHint) {
        return new NoDistinctInSQLQueryTranslatorImpl(queryIdentifier, queryString, filters, factory, entityGraphQueryHint);
    }

}

Замена для org.hibernate.hql.internal.ast.QueryTranslatorImpl:

package org.hibernate.hql.internal.ast;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.QueryException;
import org.hibernate.ScrollableResults;
import org.hibernate.engine.query.spi.EntityGraphQueryHint;
import org.hibernate.engine.spi.QueryParameters;
import org.hibernate.engine.spi.RowSelection;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.event.spi.EventSource;
import org.hibernate.hql.internal.QueryExecutionRequestException;
import org.hibernate.hql.internal.antlr.HqlSqlTokenTypes;
import org.hibernate.hql.internal.antlr.HqlTokenTypes;
import org.hibernate.hql.internal.antlr.SqlTokenTypes;
import org.hibernate.hql.internal.ast.exec.BasicExecutor;
import org.hibernate.hql.internal.ast.exec.DeleteExecutor;
import org.hibernate.hql.internal.ast.exec.MultiTableDeleteExecutor;
import org.hibernate.hql.internal.ast.exec.MultiTableUpdateExecutor;
import org.hibernate.hql.internal.ast.exec.StatementExecutor;
import org.hibernate.hql.internal.ast.tree.AggregatedSelectExpression;
import org.hibernate.hql.internal.ast.tree.FromElement;
import org.hibernate.hql.internal.ast.tree.InsertStatement;
import org.hibernate.hql.internal.ast.tree.QueryNode;
import org.hibernate.hql.internal.ast.tree.Statement;
import org.hibernate.hql.internal.ast.util.ASTPrinter;
import org.hibernate.hql.internal.ast.util.ASTUtil;
import org.hibernate.hql.internal.ast.util.NodeTraverser;
import org.hibernate.hql.spi.FilterTranslator;
import org.hibernate.hql.spi.ParameterTranslations;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.ReflectHelper;
import org.hibernate.internal.util.StringHelper;
import org.hibernate.internal.util.collections.IdentitySet;
import org.hibernate.loader.hql.QueryLoader;
import org.hibernate.param.ParameterSpecification;
import org.hibernate.persister.entity.Queryable;
import org.hibernate.type.Type;

import org.jboss.logging.Logger;

import antlr.ANTLRException;
import antlr.RecognitionException;
import antlr.TokenStreamException;
import antlr.collections.AST;

/**
 * A QueryTranslator that uses an Antlr-based parser.
 *
 * @author Joshua Davis ([email protected])
 */
public class NoDistinctInSQLQueryTranslatorImpl extends QueryTranslatorImpl implements FilterTranslator {

    private static final CoreMessageLogger LOG = Logger.getMessageLogger(
            CoreMessageLogger.class,
            QueryTranslatorImpl.class.getName()
    );

    private SessionFactoryImplementor factory;

    private final String queryIdentifier;
    private String hql;
    private boolean shallowQuery;
    private Map tokenReplacements;

    //TODO:this is only needed during compilation .. can we eliminate the instvar?
    private Map enabledFilters;

    private boolean compiled;
    private QueryLoader queryLoader;
    private StatementExecutor statementExecutor;

    private Statement sqlAst;
    private String sql;

    private ParameterTranslations paramTranslations;
    private List<ParameterSpecification> collectedParameterSpecifications;

    private EntityGraphQueryHint entityGraphQueryHint;

    /**
     * Creates a new AST-based query translator.
     *
     * @param queryIdentifier The query-identifier (used in stats collection)
     * @param query The hql query to translate
     * @param enabledFilters Currently enabled filters
     * @param factory The session factory constructing this translator instance.
     */
    public NoDistinctInSQLQueryTranslatorImpl(
            String queryIdentifier,
            String query,
            Map enabledFilters,
            SessionFactoryImplementor factory) {
        super(queryIdentifier, query, enabledFilters, factory);
        this.queryIdentifier = queryIdentifier;
        this.hql = query;
        this.compiled = false;
        this.shallowQuery = false;
        this.enabledFilters = enabledFilters;
        this.factory = factory;
    }

    public NoDistinctInSQLQueryTranslatorImpl(
            String queryIdentifier,
            String query,
            Map enabledFilters,
            SessionFactoryImplementor factory,
            EntityGraphQueryHint entityGraphQueryHint) {
        this(queryIdentifier, query, enabledFilters, factory);
        this.entityGraphQueryHint = entityGraphQueryHint;
    }

    /**
     * Compile a "normal" query. This method may be called multiple times.
     * Subsequent invocations are no-ops.
     *
     * @param replacements Defined query substitutions.
     * @param shallow Does this represent a shallow (scalar or entity-id)
     * select?
     * @throws QueryException There was a problem parsing the query string.
     * @throws MappingException There was a problem querying defined mappings.
     */
    @Override
    public void compile(
            Map replacements,
            boolean shallow) throws QueryException, MappingException {
        doCompile(replacements, shallow, null);
    }

    /**
     * Compile a filter. This method may be called multiple times. Subsequent
     * invocations are no-ops.
     *
     * @param collectionRole the role name of the collection used as the basis
     * for the filter.
     * @param replacements Defined query substitutions.
     * @param shallow Does this represent a shallow (scalar or entity-id)
     * select?
     * @throws QueryException There was a problem parsing the query string.
     * @throws MappingException There was a problem querying defined mappings.
     */
    @Override
    public void compile(
            String collectionRole,
            Map replacements,
            boolean shallow) throws QueryException, MappingException {
        doCompile(replacements, shallow, collectionRole);
    }

    /**
     * Performs both filter and non-filter compiling.
     *
     * @param replacements Defined query substitutions.
     * @param shallow Does this represent a shallow (scalar or entity-id)
     * select?
     * @param collectionRole the role name of the collection used as the basis
     * for the filter, NULL if this is not a filter.
     */
    private synchronized void doCompile(Map replacements, boolean shallow, String collectionRole) {
        // If the query is already compiled, skip the compilation.
        if (compiled) {
            LOG.debug("compile() : The query is already compiled, skipping...");
            return;
        }

        // Remember the parameters for the compilation.
        this.tokenReplacements = replacements;
        if (tokenReplacements == null) {
            tokenReplacements = new HashMap();
        }
        this.shallowQuery = shallow;

        try {
            // PHASE 1 : Parse the HQL into an AST.
            final HqlParser parser = parse(true);

            // PHASE 2 : Analyze the HQL AST, and produce an SQL AST.
            final HqlSqlWalker w = analyze(parser, collectionRole);

            sqlAst = (Statement) w.getAST();

            // at some point the generate phase needs to be moved out of here,
            // because a single object-level DML might spawn multiple SQL DML
            // command executions.
            //
            // Possible to just move the sql generation for dml stuff, but for
            // consistency-sake probably best to just move responsiblity for
            // the generation phase completely into the delegates
            // (QueryLoader/StatementExecutor) themselves.  Also, not sure why
            // QueryLoader currently even has a dependency on this at all; does
            // it need it?  Ideally like to see the walker itself given to the delegates directly...
            if (sqlAst.needsExecutor()) {
                statementExecutor = buildAppropriateStatementExecutor(w);
            } else {
                // PHASE 3 : Generate the SQL.
                generate((QueryNode) sqlAst);
                queryLoader = new QueryLoader(this, factory, w.getSelectClause());
            }

            compiled = true;
        } catch (QueryException qe) {
            if (qe.getQueryString() == null) {
                throw qe.wrapWithQueryString(hql);
            } else {
                throw qe;
            }
        } catch (RecognitionException e) {
            // we do not actually propagate ANTLRExceptions as a cause, so
            // log it here for diagnostic purposes
            LOG.trace("Converted antlr.RecognitionException", e);
            throw QuerySyntaxException.convert(e, hql);
        } catch (ANTLRException e) {
            // we do not actually propagate ANTLRExceptions as a cause, so
            // log it here for diagnostic purposes
            LOG.trace("Converted antlr.ANTLRException", e);
            throw new QueryException(e.getMessage(), hql);
        }

        //only needed during compilation phase...
        this.enabledFilters = null;
    }

    private void generate(AST sqlAst) throws QueryException, RecognitionException {
        if (sql == null) {
            final SqlGenerator gen = new SqlGenerator(factory);
            gen.statement(sqlAst);
            sql = gen.getSQL();
            //Hack: The distinct operator is removed from the sql 
            //string to avoid executing a distinct query in the db server when 
            //the distinct is used in hql.
            sql = sql.replace("distinct", "");
            if (LOG.isDebugEnabled()) {
                LOG.debugf("HQL: %s", hql);
                LOG.debugf("SQL: %s", sql);
            }
            gen.getParseErrorHandler().throwQueryException();
            collectedParameterSpecifications = gen.getCollectedParameters();
        }
    }

    private static final ASTPrinter SQL_TOKEN_PRINTER = new ASTPrinter(SqlTokenTypes.class);

    private HqlSqlWalker analyze(HqlParser parser, String collectionRole) throws QueryException, RecognitionException {
        final HqlSqlWalker w = new HqlSqlWalker(this, factory, parser, tokenReplacements, collectionRole);
        final AST hqlAst = parser.getAST();

        // Transform the tree.
        w.statement(hqlAst);

        if (LOG.isDebugEnabled()) {
            LOG.debug(SQL_TOKEN_PRINTER.showAsString(w.getAST(), "--- SQL AST ---"));
        }

        w.getParseErrorHandler().throwQueryException();

        return w;
    }

    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;
    }

    private static final ASTPrinter HQL_TOKEN_PRINTER = new ASTPrinter(HqlTokenTypes.class);

    @Override
    void showHqlAst(AST hqlAst) {
        if (LOG.isDebugEnabled()) {
            LOG.debug(HQL_TOKEN_PRINTER.showAsString(hqlAst, "--- HQL AST ---"));
        }
    }

    private void errorIfDML() throws HibernateException {
        if (sqlAst.needsExecutor()) {
            throw new QueryExecutionRequestException("Not supported for DML operations", hql);
        }
    }

    private void errorIfSelect() throws HibernateException {
        if (!sqlAst.needsExecutor()) {
            throw new QueryExecutionRequestException("Not supported for select queries", hql);
        }
    }

    @Override
    public String getQueryIdentifier() {
        return queryIdentifier;
    }

    @Override
    public Statement getSqlAST() {
        return sqlAst;
    }

    private HqlSqlWalker getWalker() {
        return sqlAst.getWalker();
    }

    /**
     * Types of the return values of an <tt>iterate()</tt> style query.
     *
     * @return an array of <tt>Type</tt>s.
     */
    @Override
    public Type[] getReturnTypes() {
        errorIfDML();
        return getWalker().getReturnTypes();
    }

    @Override
    public String[] getReturnAliases() {
        errorIfDML();
        return getWalker().getReturnAliases();
    }

    @Override
    public String[][] getColumnNames() {
        errorIfDML();
        return getWalker().getSelectClause().getColumnNames();
    }

    @Override
    public Set<Serializable> getQuerySpaces() {
        return getWalker().getQuerySpaces();
    }

    @Override
    public List list(SessionImplementor session, QueryParameters queryParameters)
            throws HibernateException {
        // Delegate to the QueryLoader...
        errorIfDML();

        final QueryNode query = (QueryNode) sqlAst;
        final boolean hasLimit = queryParameters.getRowSelection() != null && queryParameters.getRowSelection().definesLimits();
        final boolean needsDistincting = (query.getSelectClause().isDistinct() || hasLimit) && containsCollectionFetches();

        QueryParameters queryParametersToUse;
        if (hasLimit && containsCollectionFetches()) {
            LOG.firstOrMaxResultsSpecifiedWithCollectionFetch();
            RowSelection selection = new RowSelection();
            selection.setFetchSize(queryParameters.getRowSelection().getFetchSize());
            selection.setTimeout(queryParameters.getRowSelection().getTimeout());
            queryParametersToUse = queryParameters.createCopyUsing(selection);
        } else {
            queryParametersToUse = queryParameters;
        }

        List results = queryLoader.list(session, queryParametersToUse);

        if (needsDistincting) {
            int includedCount = -1;
            // NOTE : firstRow is zero-based
            int first = !hasLimit || queryParameters.getRowSelection().getFirstRow() == null
                    ? 0
                    : queryParameters.getRowSelection().getFirstRow();
            int max = !hasLimit || queryParameters.getRowSelection().getMaxRows() == null
                    ? -1
                    : queryParameters.getRowSelection().getMaxRows();
            List tmp = new ArrayList();
            IdentitySet distinction = new IdentitySet();
            for (final Object result : results) {
                if (!distinction.add(result)) {
                    continue;
                }
                includedCount++;
                if (includedCount < first) {
                    continue;
                }
                tmp.add(result);
                // NOTE : ( max - 1 ) because first is zero-based while max is not...
                if (max >= 0 && (includedCount - first) >= (max - 1)) {
                    break;
                }
            }
            results = tmp;
        }

        return results;
    }

    /**
     * Return the query results as an iterator
     */
    @Override
    public Iterator iterate(QueryParameters queryParameters, EventSource session)
            throws HibernateException {
        // Delegate to the QueryLoader...
        errorIfDML();
        return queryLoader.iterate(queryParameters, session);
    }

    /**
     * Return the query results, as an instance of <tt>ScrollableResults</tt>
     */
    @Override
    public ScrollableResults scroll(QueryParameters queryParameters, SessionImplementor session)
            throws HibernateException {
        // Delegate to the QueryLoader...
        errorIfDML();
        return queryLoader.scroll(queryParameters, session);
    }

    @Override
    public int executeUpdate(QueryParameters queryParameters, SessionImplementor session)
            throws HibernateException {
        errorIfSelect();
        return statementExecutor.execute(queryParameters, session);
    }

    /**
     * The SQL query string to be called; implemented by all subclasses
     */
    @Override
    public String getSQLString() {
        return sql;
    }

    @Override
    public List<String> collectSqlStrings() {
        ArrayList<String> list = new ArrayList<>();
        if (isManipulationStatement()) {
            String[] sqlStatements = statementExecutor.getSqlStatements();
            Collections.addAll(list, sqlStatements);
        } else {
            list.add(sql);
        }
        return list;
    }

    // -- Package local methods for the QueryLoader delegate --
    @Override
    public boolean isShallowQuery() {
        return shallowQuery;
    }

    @Override
    public String getQueryString() {
        return hql;
    }

    @Override
    public Map getEnabledFilters() {
        return enabledFilters;
    }

    @Override
    public int[] getNamedParameterLocs(String name) {
        return getWalker().getNamedParameterLocations(name);
    }

    @Override
    public boolean containsCollectionFetches() {
        errorIfDML();
        List collectionFetches = ((QueryNode) sqlAst).getFromClause().getCollectionFetches();
        return collectionFetches != null && collectionFetches.size() > 0;
    }

    @Override
    public boolean isManipulationStatement() {
        return sqlAst.needsExecutor();
    }

    @Override
    public void validateScrollability() throws HibernateException {
        // Impl Note: allows multiple collection fetches as long as the
        // entire fecthed graph still "points back" to a single
        // root entity for return

        errorIfDML();

        final QueryNode query = (QueryNode) sqlAst;

        // If there are no collection fetches, then no further checks are needed
        List collectionFetches = query.getFromClause().getCollectionFetches();
        if (collectionFetches.isEmpty()) {
            return;
        }

        // A shallow query is ok (although technically there should be no fetching here...)
        if (isShallowQuery()) {
            return;
        }

        // Otherwise, we have a non-scalar select with defined collection fetch(es).
        // Make sure that there is only a single root entity in the return (no tuples)
        if (getReturnTypes().length > 1) {
            throw new HibernateException("cannot scroll with collection fetches and returned tuples");
        }

        FromElement owner = null;
        for (Object o : query.getSelectClause().getFromElementsForLoad()) {
            // should be the first, but just to be safe...
            final FromElement fromElement = (FromElement) o;
            if (fromElement.getOrigin() == null) {
                owner = fromElement;
                break;
            }
        }

        if (owner == null) {
            throw new HibernateException("unable to locate collection fetch(es) owner for scrollability checks");
        }

        // This is not strictly true.  We actually just need to make sure that
        // it is ordered by root-entity PK and that that order-by comes before
        // any non-root-entity ordering...
        AST primaryOrdering = query.getOrderByClause().getFirstChild();
        if (primaryOrdering != null) {
            // TODO : this is a bit dodgy, come up with a better way to check this (plus see above comment)
            String[] idColNames = owner.getQueryable().getIdentifierColumnNames();
            String expectedPrimaryOrderSeq = StringHelper.join(
                    ", ",
                    StringHelper.qualify(owner.getTableAlias(), idColNames)
            );
            if (!primaryOrdering.getText().startsWith(expectedPrimaryOrderSeq)) {
                throw new HibernateException("cannot scroll results with collection fetches which are not ordered primarily by the root entity PK");
            }
        }
    }

    private StatementExecutor buildAppropriateStatementExecutor(HqlSqlWalker walker) {
        final Statement statement = (Statement) walker.getAST();
        switch (walker.getStatementType()) {
            case HqlSqlTokenTypes.DELETE: {
                final FromElement fromElement = walker.getFinalFromClause().getFromElement();
                final Queryable persister = fromElement.getQueryable();
                if (persister.isMultiTable()) {
                    return new MultiTableDeleteExecutor(walker);
                } else {
                    return new DeleteExecutor(walker, persister);
                }
            }
            case HqlSqlTokenTypes.UPDATE: {
                final FromElement fromElement = walker.getFinalFromClause().getFromElement();
                final Queryable persister = fromElement.getQueryable();
                if (persister.isMultiTable()) {
                    // even here, if only properties mapped to the "base table" are referenced
                    // in the set and where clauses, this could be handled by the BasicDelegate.
                    // TODO : decide if it is better performance-wise to doAfterTransactionCompletion that check, or to simply use the MultiTableUpdateDelegate
                    return new MultiTableUpdateExecutor(walker);
                } else {
                    return new BasicExecutor(walker, persister);
                }
            }
            case HqlSqlTokenTypes.INSERT:
                return new BasicExecutor(walker, ((InsertStatement) statement).getIntoClause().getQueryable());
            default:
                throw new QueryException("Unexpected statement type");
        }
    }

    @Override
    public ParameterTranslations getParameterTranslations() {
        if (paramTranslations == null) {
            paramTranslations = new ParameterTranslationsImpl(getWalker().getParameters());
        }
        return paramTranslations;
    }

    @Override
    public List<ParameterSpecification> getCollectedParameterSpecifications() {
        return collectedParameterSpecifications;
    }

    @Override
    public Class getDynamicInstantiationResultType() {
        AggregatedSelectExpression aggregation = queryLoader.getAggregatedSelectExpression();
        return aggregation == null ? null : aggregation.getAggregationResultType();
    }

    public static class JavaConstantConverter implements NodeTraverser.VisitationStrategy {

        private AST dotRoot;

        @Override
        public void visit(AST node) {
            if (dotRoot != null) {
                // we are already processing a dot-structure
                if (ASTUtil.isSubtreeChild(dotRoot, node)) {
                    return;
                }
                // we are now at a new tree level
                dotRoot = null;
            }

            if (node.getType() == HqlTokenTypes.DOT) {
                dotRoot = node;
                handleDotStructure(dotRoot);
            }
        }

        private void handleDotStructure(AST dotStructureRoot) {
            final String expression = ASTUtil.getPathText(dotStructureRoot);
            final Object constant = ReflectHelper.getConstantValue(expression);
            if (constant != null) {
                dotStructureRoot.setFirstChild(null);
                dotStructureRoot.setType(HqlTokenTypes.JAVA_CONSTANT);
                dotStructureRoot.setText(expression);
            }
        }
    }

    @Override
    public EntityGraphQueryHint getEntityGraphQueryHint() {
        return entityGraphQueryHint;
    }

    @Override
    public void setEntityGraphQueryHint(EntityGraphQueryHint entityGraphQueryHint) {
        this.entityGraphQueryHint = entityGraphQueryHint;
    }
}

Если вы будете следовать потоку кода, вы заметите, что я только что изменил метод private void generate(AST sqlAst) throws QueryException, RecognitionException и добавил следующие строки:

//Hack: The distinct keywordis removed from the sql string to 
//avoid executing a distinct query in the DBMS when the distinct 
//is used in hql.
sql = sql.replace("distinct", "");

Что я делаю с этим кодом, так это удалить ключевое слово из сгенерированного SQL-запроса.

После создания классов выше, я добавил следующую строку в файле конфигурации hibernate:

<property name="hibernate.query.factory_class">org.hibernate.hql.internal.ast.NoDistinctInSQLASTQueryTranslatorFactory</property>

Эта строка сообщает hibernate использовать мой пользовательский класс для анализа запросов HQL и генерации SQL-запросов без отдельного ключевого слова. Заметьте, что я создал свои собственные классы в том же пакете, где находится исходный парсер HQL.