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

private List doTheLoad(String sql, QueryParameters queryParameters, SharedSessionContractImplementor session) throws SQLException {
	final RowSelection selection = queryParameters.getRowSelection();
	final int maxRows = LimitHelper.hasMaxRows( selection ) ?
			selection.getMaxRows() :
			Integer.MAX_VALUE;

	final List<AfterLoadAction> afterLoadActions = new ArrayList<>();
	final SqlStatementWrapper wrapper = executeQueryStatement( sql, queryParameters, false, afterLoadActions, session );
	final ResultSet rs = wrapper.getResultSet();
	final Statement st = wrapper.getStatement();
	try {
		return processResultSet( rs, queryParameters, session, false, null, maxRows, afterLoadActions );
	}
	finally {
		session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( st );
		session.getJdbcCoordinator().afterStatementExecution();
	}
}
 

private void doTheLoad(String sql, QueryParameters queryParameters, SharedSessionContractImplementor session) throws SQLException {
	final RowSelection selection = queryParameters.getRowSelection();
	final int maxRows = LimitHelper.hasMaxRows( selection ) ?
			selection.getMaxRows() :
			Integer.MAX_VALUE;

	final List<AfterLoadAction> afterLoadActions = Collections.emptyList();
	final SqlStatementWrapper wrapper = executeQueryStatement( sql, queryParameters, false, afterLoadActions, session );
	final ResultSet rs = wrapper.getResultSet();
	final Statement st = wrapper.getStatement();
	try {
		processResultSet( rs, queryParameters, session, true, null, maxRows, afterLoadActions );
	}
	finally {
		session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( st );
		session.getJdbcCoordinator().afterStatementExecution();
	}
}
 

@Override
public String processSql(String sql, RowSelection selection) {
	if ( selection.getMaxRows() == null ) {
		return sql;
	}

	int top = getMaxOrLimit( selection );
	if ( top == Integer.MAX_VALUE ) {
		return sql;
	}

	Matcher selectDistinctMatcher = SELECT_DISTINCT_PATTERN.matcher( sql );
	if ( selectDistinctMatcher.matches() ) {
		return insertTop( selectDistinctMatcher, sql, top );
	}

	Matcher selectMatcher = SELECT_PATTERN.matcher( sql );
	if ( selectMatcher.matches() ) {
		return insertTop( selectMatcher, sql, top );
	}

	return sql;
}
 

private List doQuery(
			final SharedSessionContractImplementor session,
			final QueryParameters queryParameters,
			final boolean returnProxies,
			final ResultTransformer forcedResultTransformer) throws SQLException, HibernateException {

		final RowSelection selection = queryParameters.getRowSelection();
		final int maxRows = LimitHelper.hasMaxRows( selection ) ?
				selection.getMaxRows() :
				Integer.MAX_VALUE;

		final List<AfterLoadAction> afterLoadActions = new ArrayList<AfterLoadAction>();

		final SqlStatementWrapper wrapper = executeQueryStatement( queryParameters, false, afterLoadActions, session );
		final ResultSet rs = wrapper.getResultSet();
		final Statement st = wrapper.getStatement();

// would be great to move all this below here into another method that could also be used
// from the new scrolling stuff.
//
// Would need to change the way the max-row stuff is handled (i.e. behind an interface) so
// that I could do the control breaking at the means to know when to stop

		try {
			return processResultSet(
					rs,
					queryParameters,
					session,
					returnProxies,
					forcedResultTransformer,
					maxRows,
					afterLoadActions
			);
		}
		finally {
			session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( st );
			session.getJdbcCoordinator().afterStatementExecution();
		}

	}
 

/**
 * If we're able to guess a likely size of the results we can optimize allocation
 * of our datastructures.
 * Essentially if we detect the user is not using pagination, we attempt to use the FetchSize
 * as a reasonable hint. If fetch size is not being set either, it is reasonable to expect
 * that we're going to have a single hit. In such a case it would be tempting to return a constant
 * of value one, but that's dangerous as it doesn't scale up appropriately for example
 * with an ArrayList if the guess is wrong.
 *
 * @param rowSelection
 * @return a reasonable size to use for allocation
 */
@SuppressWarnings("UnnecessaryUnboxing")
private int guessResultSize(RowSelection rowSelection) {
	if ( rowSelection != null ) {
		final int maxReasonableAllocation = rowSelection.getFetchSize() != null ? rowSelection.getFetchSize().intValue() : 100;
		if ( rowSelection.getMaxRows() != null && rowSelection.getMaxRows().intValue() > 0 ) {
			return Math.min( maxReasonableAllocation, rowSelection.getMaxRows().intValue() );
		}
		else if ( rowSelection.getFetchSize() != null && rowSelection.getFetchSize().intValue() > 0 ) {
			return rowSelection.getFetchSize().intValue();
		}
	}
	return 7;//magic number guessed as a reasonable default.
}
 

/**
 * Some dialect-specific LIMIT clauses require the maximum last row number
 * (aka, first_row_number + total_row_count), while others require the maximum
 * returned row count (the total maximum number of rows to return).
 *
 * @param selection the selection criteria for rows.
 *
 * @return The appropriate value to bind into the limit clause.
 */
protected final int getMaxOrLimit(RowSelection selection) {
	final int firstRow = convertToFirstRowValue( LimitHelper.getFirstRow( selection ) );
	final int lastRow = selection.getMaxRows();
	final int maxRows = useMaxForLimit() ? lastRow + firstRow : lastRow;
	// Use Integer.MAX_VALUE on overflow
	if ( maxRows < 0 ) {
		return Integer.MAX_VALUE;
	}
	else {
		return maxRows;
	}
}
 

@Override
public void setMaxRows(RowSelection selection, PreparedStatement statement) throws SQLException {
	if ( LimitHelper.hasMaxRows( selection ) ) {
		int maxRows = selection.getMaxRows() + convertToFirstRowValue( LimitHelper.getFirstRow( selection ) );
		// Use Integer.MAX_VALUE on overflow
		if ( maxRows < 0 ) {
			statement.setMaxRows( Integer.MAX_VALUE );
		}
		else {
			statement.setMaxRows( maxRows );
		}
	}
}
 

@Override
public List extractResults(
		ResultSet resultSet,
		final SharedSessionContractImplementor session,
		QueryParameters queryParameters,
		NamedParameterContext namedParameterContext,
		boolean returnProxies,
		boolean readOnly,
		ResultTransformer forcedResultTransformer,
		List<AfterLoadAction> afterLoadActionList) throws SQLException {

	handlePotentiallyEmptyCollectionRootReturns( loadPlan, queryParameters.getCollectionKeys(), resultSet, session );

	final int maxRows;
	final RowSelection selection = queryParameters.getRowSelection();
	if ( LimitHelper.hasMaxRows( selection ) ) {
		maxRows = selection.getMaxRows();
		LOG.tracef( "Limiting ResultSet processing to just %s rows", maxRows );
	}
	else {
		maxRows = Integer.MAX_VALUE;
	}

	// Handles the "FETCH ALL PROPERTIES" directive in HQL
	final boolean forceFetchLazyAttributes = false;

	final ResultSetProcessingContextImpl context = new ResultSetProcessingContextImpl(
			resultSet,
			session,
			loadPlan,
			aliasResolutionContext,
			readOnly,
			shouldUseOptionalEntityInstance,
			forceFetchLazyAttributes,
			returnProxies,
			queryParameters,
			namedParameterContext,
			hadSubselectFetches
	);

	final List loadResults = new ArrayList();

	LOG.trace( "Processing result set" );
	int count;
	for ( count = 0; count < maxRows && resultSet.next(); count++ ) {
		LOG.debugf( "Starting ResultSet row #%s", count );

		Object logicalRow = rowReader.readRow( resultSet, context );

		// todo : apply transformers here?

		loadResults.add( logicalRow );

		context.finishUpRow();
	}

	LOG.tracev( "Done processing result set ({0} rows)", count );

	rowReader.finishUp( context, afterLoadActionList );
	context.wrapUp();

	session.getPersistenceContext().initializeNonLazyCollections();

	return loadResults;
}
 

/**
 * Generates a QueryKey.
 *
 * @param queryString The sql query string.
 * @param queryParameters The query parameters
 * @param filterKeys The keys of any enabled filters.
 * @param session The current session.
 * @param customTransformer The result transformer; should be null if data is not transformed before being cached.
 *
 * @return The generate query cache key.
 */
public static QueryKey generateQueryKey(
		String queryString,
		QueryParameters queryParameters,
		Set filterKeys,
		SharedSessionContractImplementor session,
		CacheableResultTransformer customTransformer) {
	// disassemble positional parameters
	final int positionalParameterCount = queryParameters.getPositionalParameterTypes().length;
	final Type[] types = new Type[positionalParameterCount];
	final Object[] values = new Object[positionalParameterCount];
	for ( int i = 0; i < positionalParameterCount; i++ ) {
		types[i] = queryParameters.getPositionalParameterTypes()[i];
		values[i] = types[i].disassemble( queryParameters.getPositionalParameterValues()[i], session, null );
	}

	// disassemble named parameters
	final Map<String,TypedValue> namedParameters;
	if ( queryParameters.getNamedParameters() == null ) {
		namedParameters = null;
	}
	else {
		namedParameters = CollectionHelper.mapOfSize( queryParameters.getNamedParameters().size() );
		for ( Map.Entry<String,TypedValue> namedParameterEntry : queryParameters.getNamedParameters().entrySet() ) {
			namedParameters.put(
					namedParameterEntry.getKey(),
					new TypedValue(
							namedParameterEntry.getValue().getType(),
							namedParameterEntry.getValue().getType().disassemble(
									namedParameterEntry.getValue().getValue(),
									session,
									null
							)
					)
			);
		}
	}

	// decode row selection...
	final RowSelection selection = queryParameters.getRowSelection();
	final Integer firstRow;
	final Integer maxRows;
	if ( selection != null ) {
		firstRow = selection.getFirstRow();
		maxRows = selection.getMaxRows();
	}
	else {
		firstRow = null;
		maxRows = null;
	}

	return new QueryKey(
			queryString,
			types,
			values,
			namedParameters,
			firstRow,
			maxRows,
			filterKeys,
			session.getTenantIdentifier(),
			customTransformer
	);
}
 

/**
 * Is a max row limit indicated?
 *
 * @param selection The row selection options
 *
 * @return Whether a max row limit was indicated
 */
public static boolean hasMaxRows(RowSelection selection) {
	return selection != null && selection.getMaxRows() != null && selection.getMaxRows() > 0;
}