Example usage for org.hibernate.criterion Projection isGrouped

Introduction

In this page you can find the example usage for org.hibernate.criterion Projection isGrouped.

Prototype

public boolean isGrouped();

Source Link

Document

Is this projection fragment (SELECT clause) also part of the GROUP BY

Usage

From source file:org.candlepin.model.DetachedCandlepinQuery.java

License:Open Source License

/**
 * {@inheritDoc}/*from www  .j  a  v  a 2s. c  o m*/
 */
@Override
@SuppressWarnings({ "unchecked", "checkstyle:indentation" })
public int getRowCount() {
    CriteriaImpl executable = (CriteriaImpl) this.getExecutableCriteria();

    // Impl note:
    // We're using the projection method here over using a cursor to scroll the results due to
    // limitations on various connectors' cursor implementations. Some don't properly support
    // fast-forwarding/jumping (Oracle) and others fake the whole thing by running the query
    // and pretending to scroll (MySQL). Until these are addressed, the hack below is going to
    // be far more performant and significantly safer (which makes me sad).

    // Remove any ordering that may be applied (since we almost certainly won't have the field
    // available anymore)
    for (Iterator iterator = executable.iterateOrderings(); iterator.hasNext();) {
        iterator.next();
        iterator.remove();
    }

    Projection projection = executable.getProjection();
    if (projection != null && projection.isGrouped()) {
        // We have a projection that alters the grouping of the query. We need to rebuild the
        // projection such that it gets our row count and properly applies the group by
        // statement.
        // The logic for this block is largely derived from this Stack Overflow posting:
        // http://stackoverflow.com/
        //     questions/32498229/hibernate-row-count-on-criteria-with-already-set-projection
        //
        // A safer alternative may be to generate a query that uses the given criteria as a
        // subquery (SELECT count(*) FROM (<criteria SQL>)), but is probably less performant
        // than this hack.
        CriteriaQueryTranslator translator = new CriteriaQueryTranslator(
                (SessionFactoryImplementor) this.session.getSessionFactory(), executable,
                executable.getEntityOrClassName(), CriteriaQueryTranslator.ROOT_SQL_ALIAS);

        executable.setProjection(
                Projections.projectionList().add(Projections.rowCount()).add(Projections.sqlGroupProjection(
                        "count(count(1))", translator.getGroupBy(), new String[] {}, new Type[] {})));
    } else {
        executable.setProjection(Projections.rowCount());
    }

    Long count = (Long) executable.uniqueResult();
    return count != null ? count.intValue() : 0;
}

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