org.hibernate.engine.spi.RowSelection#setMaxRows ( )源码实例Demo

private Query createQuery() {
    Query jpaQuery = createBaseQuery();

    if (range != null) {
        jpaQuery.setFirstResult(range.getStartIndex());
        // range is 0 based, so we add 1
        jpaQuery.setMaxResults(range.getLastIndex() - range.getStartIndex() + 1);
    } else if (page != null) {
        jpaQuery.setFirstResult(page.index * page.size);
        jpaQuery.setMaxResults(page.size);
    } else {
        // Use deprecated API in org.hibernate.Query that will be moved to org.hibernate.query.Query on Hibernate 6.0
        @SuppressWarnings("deprecation")
        RowSelection options = jpaQuery.unwrap(org.hibernate.query.Query.class).getQueryOptions();
        options.setFirstRow(null);
        options.setMaxRows(null);
    }

    return jpaQuery;
}
 

@Test
public void testLimit() {
    RowSelection rowSelection = new RowSelection();
    rowSelection.setMaxRows(getMaxRows());
    long startNanos = System.nanoTime();
    doInJDBC(connection -> {
        try (PreparedStatement statement = connection.prepareStatement(SELECT_POST)
        ) {
            statement.setMaxRows(getMaxRows());
            assertEquals(getMaxRows(), processResultSet(statement));
        } catch (SQLException e) {
            fail(e.getMessage());
        }

    });
    LOGGER.info("{} Result Set with limit took {} millis",
            dataSourceProvider().database(),
            TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos));
}
 

@Test
public void testLimit() {
    RowSelection rowSelection = new RowSelection();
    rowSelection.setMaxRows(getMaxRows());
    long startNanos = System.nanoTime();
    doInJDBC(connection -> {
        try (PreparedStatement statement1 = connection.prepareStatement(SELECT_POST_COMMENT_1);
             PreparedStatement statement11 = connection.prepareStatement(SELECT_POST_COMMENT_1);
             PreparedStatement statement2 = connection.prepareStatement(SELECT_POST_COMMENT_2);
        ) {
            statement1.setMaxRows(getMaxRows());
            assertEquals(getMaxRows(), processResultSet(statement1));
            assertEquals(getPostCommentCount() * getPostCount(), processResultSet(statement11));
            assertEquals(getPostCommentCount() * getPostCount(), processResultSet(statement2));
        } catch (SQLException e) {
            fail(e.getMessage());
        }

    });
    LOGGER.info("{} Result Set with limit took {} millis",
            dataSourceProvider().database(),
            TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos));
}
 

@Test
public void testLimit() {
    final RowSelection rowSelection = new RowSelection();
    rowSelection.setMaxRows(getMaxRows());
    LimitHandler limitHandler = ((SessionFactoryImpl) sessionFactory()).getDialect().getLimitHandler();
    String limitStatement = limitHandler.processSql(SELECT_POST_COMMENT, rowSelection);
    long startNanos = System.nanoTime();
    doInJDBC(connection -> {
        try (PreparedStatement statement = connection.prepareStatement(limitStatement)) {
            limitHandler.bindLimitParametersAtEndOfQuery(rowSelection, statement, 1);
            statement.setInt(1, getMaxRows());
            statement.execute();
            int count = 0;
            ResultSet resultSet = statement.getResultSet();
            while (resultSet.next()) {
                resultSet.getLong(1);
                count++;
            }
            assertEquals(getMaxRows(), count);
        } catch (SQLException e) {
            fail(e.getMessage());
        }

    });
    LOGGER.info("{} Result Set with limit took {} millis",
            dataSourceProvider().database(),
            TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos));
}