/**
* Filter the output of the constraint for the specified column and only return results that have
* the specified value.
*
* @param constraint
* @param columns to match against
* @return a filtered list of key-values
*/
private List<CKeyValue> filterConstraint(Result toFilter, CColumn columns) {
// if there are no results, just return an empty list
if (!toFilter.getKeyValues().iterator().hasNext()) return Collections.EMPTY_LIST;
List<CKeyValue> rows = new ArrayList<CKeyValue>();
LexicographicByteArrayComparator comparator = LexicographicByteArrayComparator.INSTANCE;
for (CKeyValue kv : toFilter.getKeyValues()) {
// if we are accepting all CFs
if (comparator.compare(CColumn.ALL_COLUMNS.getColumnFamily(), columns.getColumnFamily()) == 0)
rows.add(kv);
// since we aren't accepting all CFs, check the stored against the sent
if (comparator.compare(columns.getColumnFamily(), kv.getFamily()) == 0) {
// if we are accepting all CQs
if (comparator.compare(
CColumn.ALL_COLUMNS.getColumnQualifier(), columns.getColumnQualifier())
== 0) rows.add(kv);
// since we aren't accepting all CQs, check the stored against the sent
if (comparator.compare(columns.getColumnQualifier(), kv.getQualifier()) == 0) rows.add(kv);
}
}
return rows;
}
/*
* This is now running over a table with the form: rowID = value to join on CF
* = filteredTableName.rowID CQ = the row ID.
*/
@Override
public Void call(Object... args) throws Exception {
// create the table to write the output results
final TableAdapter output = (TableAdapter) args[0];
// name of the column in the output table for the remote values
final byte[] rightOutputColumnName = (byte[]) args[1];
// constraint on the remote table
Constraint rightConstraint = (Constraint) args[2];
// the columns to get from the remote results/table
final CColumn rightColumns = (CColumn) args[3];
// get iterator over the results, after selecting the desired columns
Iterator<Result> remoteResults = rightConstraint.getResultIterator();
final LocalTableAdapter localTable = this.getLocalTableAdapter();
// if there are no values in the remote iterator, we can stop scanning the
// local table
while (remoteResults.hasNext()) {
// get the remote value
Result remoteResult = remoteResults.next();
for (CKeyValue remoteValue : this.filterConstraint(remoteResult, rightColumns)) {
// now check to see if we stored this value as a key
Iterator<Result> localResults = localTable.get(new Get(new CRange(remoteValue.getValue())));
// if there is a result (only checking the first since we are guaranteed
// a single CF, CQ at this point
if (localResults.hasNext()) {
// create the returned results
Result localRow = localResults.next();
CKeyValue remoteRow =
new CKeyValue(localRow.getRecordId(), rightOutputColumnName, remoteValue.getRowId());
output.put(new Put(remoteRow));
}
}
}
return null;
}