How to use

FromClause

in

org.apache.metamodel.query

/**
 * Gets the alias of a table, if it is registered (and visible, ie. not part
 * of a sub-query) in the FromClause
 * 
 * @param table
 *            the table to get the alias for
 * @return the alias or null if none is found
 */
public String getAlias(Table table) {
  if (table != null) {
    for (FromItem item : getItems()) {
      String alias = item.getAlias(table);
      if (alias != null) {
        return alias;
      }
    }
  }
  return null;
}

private void replaceParametersInFromClause(Object[] values, AtomicInteger parameterIndex, Query originalQuery,
    Query newQuery) {
  final List<FromItem> fromItems = originalQuery.getFromClause().getItems();
  int i = 0;
  for (FromItem fromItem : fromItems) {
    final Query subQuery = fromItem.getSubQuery();
    if (subQuery != null) {
      final Query newSubQuery = newQuery.getFromClause().getItem(i).getSubQuery();
      replaceParametersInQuery(values, parameterIndex, subQuery, newSubQuery);
      newQuery.getFromClause().removeItem(i);
      newQuery.getFromClause().addItem(i, new FromItem(newSubQuery).setAlias(fromItem.getAlias()));
    }
    i++;
  }
}

protected String rewriteFromClause(Query query, FromClause fromClause) {
  StringBuilder sb = new StringBuilder();
  if (fromClause.getItemCount() > 0) {
    sb.append(AbstractQueryClause.PREFIX_FROM);
    List<FromItem> items = fromClause.getItems();
    for (int i = 0; i < items.size(); i++) {
      FromItem item = items.get(i);
      if (i != 0) {
        sb.append(AbstractQueryClause.DELIM_COMMA);
      }
      sb.append(rewriteFromItem(query, item));
    }
  }
  return sb.toString();
}

/**
 * Retrieves a table by it's reference which may be it's alias or it's
 * qualified table name. Typically, this method is used to resolve a
 * SelectItem with a reference like "foo.bar", where "foo" may either be an
 * alias or a table name
 * 
 * @param reference
 * @return a FromItem which matches the provided reference string
 */
public FromItem getItemByReference(String reference) {
  if (reference == null) {
    return null;
  }
  for (final FromItem item : getItems()) {
    FromItem result = getItemByReference(item, reference);
    if (result != null) {
      return result;
    }
  }
  return null;
}

@Override
public DataSet executeQuery(final Query query) {
  final List<SelectItem> selectItems = query.getSelectClause().getItems();
  final List<FromItem> fromItems = query.getFromClause().getItems();
  final List<FilterItem> whereItems = query.getWhereClause().getItems();
  final List<SelectItem> whereSelectItems = query.getWhereClause().getEvaluatedSelectItems();
  if (singleFromItem && noGrouping) {
    final FromItem fromItem = query.getFromClause().getItem(0);
    final Table table = MetaModelHelper.resolveTable(fromItem);
    if (table != null) {

  final String prefix = expression.substring(0, splitIndex);
  columnName = expression.substring(splitIndex + 1);
  fromItem = _query.getFromClause().getItemByReference(prefix);
if (_query.getFromClause().getItemCount() == 1) {
  fromItem = _query.getFromClause().getItem(0);
  columnName = expression;
} else {

private List<Query> splitQueryBasedOnSubQueries(int fromItemIndex) {
  Query subQuery = _query.getFromClause().getItem(fromItemIndex).getSubQuery();
  QuerySplitter subQuerySplitter = new QuerySplitter(_dataContext, subQuery);
  subQuerySplitter.setMaxRows(_maxRows);
  List<Query> splitQueries = subQuerySplitter.splitQuery();
  List<Query> result = new ArrayList<Query>(splitQueries.size());
  for (Query splitQuery : splitQueries) {
    Query newQuery = _query.clone();
    FromClause fromClause = newQuery.getFromClause();
    String alias = fromClause.getItem(fromItemIndex).getAlias();
    fromClause.removeItem(fromItemIndex);
    newQuery.from(new FromItem(splitQuery).setAlias(alias));
    result.add(newQuery);
  }
  return result;
}

/**
 * Creates a clone of the {@link SelectItem} for use within a cloned {@link Query}.
 * 
 * @param clonedQuery a new {@link Query} object that represents the clone-to-be of a query. It is expected that
 *            {@link FromItem}s have already been cloned in this {@link Query}.
 * @return
 */
protected SelectItem clone(Query clonedQuery) {
  final SelectItem subQuerySelectItem = (_subQuerySelectItem == null ? null : _subQuerySelectItem.clone());
  final FromItem fromItem;
  if (_fromItem == null) {
    fromItem = null;
  } else if (clonedQuery != null && _query != null) {
    final int indexOfFromItem = _query.getFromClause().indexOf(_fromItem);
    if (indexOfFromItem != -1) {
      fromItem = clonedQuery.getFromClause().getItem(indexOfFromItem);
    } else {
      fromItem = _fromItem.clone();
    }
  } else {
    fromItem = _fromItem.clone();
  }
  final SelectItem s = new SelectItem(_column, fromItem, _function, _functionParameters, _expression,
      subQuerySelectItem, _alias, _functionApproximationAllowed);
  return s;
}

@Override
public SatisfiedFromBuilder on(Column left, Column right) throws IllegalArgumentException {
  if (left == null) {
    throw new IllegalArgumentException("left cannot be null");
  }
  if (right == null) {
    throw new IllegalArgumentException("right cannot be null");
  }
  getQuery().getFromClause().removeItem(leftItem);
  SelectItem[] leftOn = new SelectItem[] { new SelectItem(left) };
  SelectItem[] rightOn = new SelectItem[] { new SelectItem(right) };
  FromItem fromItem = new FromItem(joinType, leftItem, rightItem, leftOn, rightOn);
  getQuery().from(fromItem);
  return this;
}

public Query() {
  _selectClause = new SelectClause(this);
  _fromClause = new FromClause(this);
  _whereClause = new FilterClause(this, AbstractQueryClause.PREFIX_WHERE);
  _groupByClause = new GroupByClause(this);
  _havingClause = new FilterClause(this, AbstractQueryClause.PREFIX_HAVING);
  _orderByClause = new OrderByClause(this);
}

@Override
public DataSet executeQuery(final Query query) {
  final List<SelectItem> selectItems = query.getSelectClause().getItems();
  final List<FromItem> fromItems = query.getFromClause().getItems();
  final List<FilterItem> whereItems = query.getWhereClause().getItems();
  final List<SelectItem> whereSelectItems = query.getWhereClause().getEvaluatedSelectItems();
  if (singleFromItem && noGrouping) {
    final FromItem fromItem = query.getFromClause().getItem(0);
    final Table table = MetaModelHelper.resolveTable(fromItem);
    if (table != null) {

/**
 * Retrieves a table by it's reference which may be it's alias or it's
 * qualified table name. Typically, this method is used to resolve a
 * SelectItem with a reference like "foo.bar", where "foo" may either be an
 * alias or a table name
 * 
 * @param reference
 * @return a FromItem which matches the provided reference string
 */
public FromItem getItemByReference(String reference) {
  if (reference == null) {
    return null;
  }
  for (final FromItem item : getItems()) {
    FromItem result = getItemByReference(item, reference);
    if (result != null) {
      return result;
    }
  }
  return null;
}

  final String prefix = expression.substring(0, splitIndex);
  columnName = expression.substring(splitIndex + 1);
  fromItem = _query.getFromClause().getItemByReference(prefix);
if (_query.getFromClause().getItemCount() == 1) {
  fromItem = _query.getFromClause().getItem(0);
  columnName = expression;
} else {

private List<Query> splitQueryBasedOnSubQueries(int fromItemIndex) {
  Query subQuery = _query.getFromClause().getItem(fromItemIndex).getSubQuery();
  QuerySplitter subQuerySplitter = new QuerySplitter(_dataContext, subQuery);
  subQuerySplitter.setMaxRows(_maxRows);
  List<Query> splitQueries = subQuerySplitter.splitQuery();
  List<Query> result = new ArrayList<Query>(splitQueries.size());
  for (Query splitQuery : splitQueries) {
    Query newQuery = _query.clone();
    FromClause fromClause = newQuery.getFromClause();
    String alias = fromClause.getItem(fromItemIndex).getAlias();
    fromClause.removeItem(fromItemIndex);
    newQuery.from(new FromItem(splitQuery).setAlias(alias));
    result.add(newQuery);
  }
  return result;
}

/**
 * Creates a clone of the {@link SelectItem} for use within a cloned {@link Query}.
 * 
 * @param clonedQuery a new {@link Query} object that represents the clone-to-be of a query. It is expected that
 *            {@link FromItem}s have already been cloned in this {@link Query}.
 * @return
 */
protected SelectItem clone(Query clonedQuery) {
  final SelectItem subQuerySelectItem = (_subQuerySelectItem == null ? null : _subQuerySelectItem.clone());
  final FromItem fromItem;
  if (_fromItem == null) {
    fromItem = null;
  } else if (clonedQuery != null && _query != null) {
    final int indexOfFromItem = _query.getFromClause().indexOf(_fromItem);
    if (indexOfFromItem != -1) {
      fromItem = clonedQuery.getFromClause().getItem(indexOfFromItem);
    } else {
      fromItem = _fromItem.clone();
    }
  } else {
    fromItem = _fromItem.clone();
  }
  final SelectItem s = new SelectItem(_column, fromItem, _function, _functionParameters, _expression,
      subQuerySelectItem, _alias, _functionApproximationAllowed);
  return s;
}

@Override
public SatisfiedFromBuilder on(Column left, Column right) throws IllegalArgumentException {
  if (left == null) {
    throw new IllegalArgumentException("left cannot be null");
  }
  if (right == null) {
    throw new IllegalArgumentException("right cannot be null");
  }
  getQuery().getFromClause().removeItem(leftItem);
  SelectItem[] leftOn = new SelectItem[] { new SelectItem(left) };
  SelectItem[] rightOn = new SelectItem[] { new SelectItem(right) };
  FromItem fromItem = new FromItem(joinType, leftItem, rightItem, leftOn, rightOn);
  getQuery().from(fromItem);
  return this;
}

public Query() {
  _selectClause = new SelectClause(this);
  _fromClause = new FromClause(this);
  _whereClause = new FilterClause(this, AbstractQueryClause.PREFIX_WHERE);
  _groupByClause = new GroupByClause(this);
  _havingClause = new FilterClause(this, AbstractQueryClause.PREFIX_HAVING);
  _orderByClause = new OrderByClause(this);
}

/**
 * Gets the alias of a table, if it is registered (and visible, ie. not part
 * of a sub-query) in the FromClause
 * 
 * @param table
 *            the table to get the alias for
 * @return the alias or null if none is found
 */
public String getAlias(Table table) {
  if (table != null) {
    for (FromItem item : getItems()) {
      String alias = item.getAlias(table);
      if (alias != null) {
        return alias;
      }
    }
  }
  return null;
}

private void replaceParametersInFromClause(Object[] values, AtomicInteger parameterIndex, Query originalQuery,
    Query newQuery) {
  final List<FromItem> fromItems = originalQuery.getFromClause().getItems();
  int i = 0;
  for (FromItem fromItem : fromItems) {
    final Query subQuery = fromItem.getSubQuery();
    if (subQuery != null) {
      final Query newSubQuery = newQuery.getFromClause().getItem(i).getSubQuery();
      replaceParametersInQuery(values, parameterIndex, subQuery, newSubQuery);
      newQuery.getFromClause().removeItem(i);
      newQuery.getFromClause().addItem(i, new FromItem(newSubQuery).setAlias(fromItem.getAlias()));
    }
    i++;
  }
}

protected String rewriteFromClause(Query query, FromClause fromClause) {
  StringBuilder sb = new StringBuilder();
  if (fromClause.getItemCount() > 0) {
    sb.append(AbstractQueryClause.PREFIX_FROM);
    List<FromItem> items = fromClause.getItems();
    for (int i = 0; i < items.size(); i++) {
      FromItem item = items.get(i);
      if (i != 0) {
        sb.append(AbstractQueryClause.DELIM_COMMA);
      }
      sb.append(rewriteFromItem(query, item));
    }
  }
  return sb.toString();
}