我正在寻找代码示例来检索列族的所有行和所有列。就像是: SELECT * FROM MyTable 我看到这可以使用RangeSlicesQuery完成,但您仍然需要提供一定的范围。而且我想你也必须指定列名。有没有
SELECT * FROM MyTable
我看到这可以使用RangeSlicesQuery完成,但您仍然需要提供一定的范围。而且我想你也必须指定列名。有没有一个干净和安全的方式来做到这一点?
使用Hector 1.0和Cassandra 1.0。
尝试这样的东西:public class Dumper {
private final Cluster cluster;
private final Keyspace keyspace;
public Dumper() {
this.cluster = HFactory.getOrCreateCluster("Name", "hostname");
this.keyspace = HFactory.createKeyspace("Keyspace", cluster, new QuorumAllConsistencyLevelPolicy());
}
public void run() {
int row_count = 100;
RangeSlicesQuery<UUID, String, Long> rangeSlicesQuery = HFactory
.createRangeSlicesQuery(keyspace, UUIDSerializer.get(), StringSerializer.get(), LongSerializer.get())
.setColumnFamily("Column Family")
.setRange(null, null, false, 10)
.setRowCount(row_count);
UUID last_key = null;
while (true) {
rangeSlicesQuery.setKeys(last_key, null);
System.out.println(" > " + last_key);
QueryResult<OrderedRows<UUID, String, Long>> result = rangeSlicesQuery.execute();
OrderedRows<UUID, String, Long> rows = result.get();
Iterator<Row<UUID, String, Long>> rowsIterator = rows.iterator();
// we'll skip this first one, since it is the same as the last one from previous time we executed
if (last_key != null && rowsIterator != null) rowsIterator.next();
while (rowsIterator.hasNext()) {
Row<UUID, String, Long> row = rowsIterator.next();
last_key = row.getKey();
if (row.getColumnSlice().getColumns().isEmpty()) {
continue;
}
System.out.println(row);
}
if (rows.getCount() < row_count)
break;
}
}
public static void main(String[] args) {
new Dumper().run();
}
}
这将在100行的页面中查看列系列。它将只为每行提取10列(您也将要打印非常长的行)。
这是一个列系列,其中有uuids用于行键,用于列名称的字符串和值的长度。希望明白如何改变这一点。
