CassandraTableHandle tableHandle = table.getTableHandle();
String schemaName = tableHandle.getSchemaName();
List<CassandraColumnHandle> partitionKeyColumns = table.getPartitionKeyColumns();
boolean fullPartitionKey = filterPrefix.size() == partitionKeyColumns.size();
ResultSetFuture countFuture;
if (!fullPartitionKey) {
final Select countAll = CassandraCqlUtils.selectCountAllFrom(tableHandle).limit(limitForPartitionKeySelect);
countFuture = executeWithSession(schemaName, new SessionCallable<ResultSetFuture>() {
@Override
public ResultSetFuture executeWithSession(Session session)
{
return session.executeAsync(countAll);
}
});
}
else {
// no need to count if partition key is completely known
countFuture = null;
}
int limit = fullPartitionKey ? 1 : limitForPartitionKeySelect;
final Select partitionKeys = CassandraCqlUtils.selectDistinctFrom(tableHandle, partitionKeyColumns);
partitionKeys.limit(limit);
partitionKeys.setFetchSize(fetchSizeForPartitionKeySelect);
if (!fullPartitionKey) {
addWhereClause(partitionKeys.where(), partitionKeyColumns, new ArrayList<Comparable<?>>());
ResultSetFuture partitionKeyFuture = executeWithSession(schemaName, new SessionCallable<ResultSetFuture>() {
@Override
public ResultSetFuture executeWithSession(Session session)
{
return session.executeAsync(partitionKeys);
}
});
long count = countFuture.getUninterruptibly().one().getLong(0);
if (count == limitForPartitionKeySelect) {
partitionKeyFuture.cancel(true);
return null; // too much effort to query all partition keys
}
else {
return partitionKeyFuture.getUninterruptibly();
}
}
else {
addWhereClause(partitionKeys.where(), partitionKeyColumns, filterPrefix);
ResultSetFuture partitionKeyFuture = executeWithSession(schemaName, new SessionCallable<ResultSetFuture>() {
@Override
public ResultSetFuture executeWithSession(Session session)
{
return session.executeAsync(partitionKeys);
}
});
return partitionKeyFuture.getUninterruptibly();
}
}