/**
* Columns from USING expression are unqualified. In case of INNER join, it doesn't matter we can
* pick the first table which contains the input column. In case of OUTER joins, we must the OUTER
* table - if it's a null-able column the outer join must return them.
*
* @param columnName
* @return table name this column belongs to
*/
protected void resolveUsingColumns(VoltXMLElement columns, RangeVariable[] rvs)
throws HSQLParseException {
// Only one OUTER join for a whole select is supported so far
for (VoltXMLElement columnElmt : columns.children) {
boolean innerJoin = true;
String table = null;
if (columnElmt.attributes.get("table") == null) {
for (RangeVariable rv : rvs) {
if (rv.isLeftJoin || rv.isRightJoin) {
if (innerJoin == false) {
throw new HSQLParseException(
"VoltDB does not support outer joins with more than two tables involved");
}
innerJoin = false;
}
if (!rv.getTable().columnList.containsKey(columnElmt.attributes.get("column"))) {
// The column is not from this table. Skip it
continue;
}
// If there is an OUTER join we need to pick the outer table
if (rv.isRightJoin == true) {
// this is the outer table. no need to search further.
table = rv.getTable().getName().name;
break;
} else if (rv.isLeftJoin == false) {
// it's the inner join. we found the table but still need to iterate
// just in case there is an outer table we haven't seen yet.
table = rv.getTable().getName().name;
}
}
if (table != null) {
columnElmt.attributes.put("table", table);
}
}
}
}
