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Simplehbase is a lightweight ORM framework between java app and hbase.
scan时指定的qualifier应该考虑filter中的qualifier和DO中的column定义。
否则
1 性能差。导致大量无用数据返回,如DO只是映射了一个family中个别字段。
2 功能不正常。我记着有个地方说是scan的qualifier和filter的qualifier不一致,有可能导致filter不执行。
simplehbase有计划支持 1.2., 1.3. 等版本吗?
RT
简单看了下ppt中举的例子,发现个问题:rowkey存储的数据,貌似在qualifier里面也存储了一份。是么?
最近在看antlr4,在写g4文件
作者可以开源看下吗 ?
client指定ts时,有可能client和hbase的时间不同步,导致混乱。
因此,应该尽量避免使用client ts。
如果使用client ts,应该设法保证该row就不要再使用hbase ts,避免时序混乱。
老版本的hbase count时可以用不存在的列count,结果是包含该行的。
较新版本的hbase count时用不存在的列count,结果是0。
@Test
public void testCount_NonExistColumn() throws Throwable {
LongColumnInterpreter columnInterpreter = new LongColumnInterpreter();
AggregationClient aggregationClient = new AggregationClient(
Config.getConfiguration());
Scan scan = new Scan();
scan.addColumn(ColumnFamilyName, QName_NotExistColumn);
Long count = aggregationClient.rowCount(TableNameBytes,
columnInterpreter, scan);
// Assert.assertTrue(count.longValue() == 4);
Assert.assertTrue(count.longValue() == 0);
}
Scan with filter
使用scan.addColumn()时
0.94.0 0.94.9 一致
0.94.24和其他版本不一致
在0.94.0 0.94.9 中,当scan.addColumn()时,无论该column是否和filter中的column一致,该filter都是生效的。
区别在于返回的行不同。
当addColumn为Q1,先选择出
rowkey f/q1 f/q2 f/q3
1 1 2
2 4 8
3 16
5 64 NULL
6 NULL 128
7 NULL NULL
然后filter出
rowkey f/q1 f/q2 f/q3
2 4 8
3 16
5 64 NULL
当addColumn为Q2,先选择出
rowkey f/q1 f/q2 f/q3
1 1 2
2 4 8
4 32
5 64 NULL
6 NULL 128
7 NULL NULL
然后filter出
rowkey f/q1 f/q2 f/q3
2 4 8
4 32
5 64 NULL
在0.94.24和0.98.8中,当scan.addColumn()时,如果column和filter中的column不一致,该filter不生效的。
当addColumn为Q2,先选择出
rowkey f/q1 f/q2 f/q3
1 1 2
2 4 8
4 32
5 64 NULL
6 NULL 128
7 NULL NULL
然后filter不生效,返回结果。
使用scan.addFamily()时
3个版本功能一致。
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