如何从 HBase 中的某一行和某一列获取多个版本

Question

我们知道，hbase有一个特性，就是特定的Row和特定的Column可以通过时间戳记录最近的变化值。 所以我的问题是，如何使用任何 HBase 命令列出所有更改的值？我用谷歌搜索了很多，但没有找到任何有用的链接。

Answer 1

默认情况下不启用版本控制。所以你在创建表时指定了它。

create 'student',{NAME=>"personal",Versions=>5},'school'

此处为“个人”列启用了版本控制，但未为“学校”列启用了版本控制。

如果您描述表“对于 personal”，则可以看到

hbase(main):009:0> describe 'student'
Table student is ENABLED
student
COLUMN FAMILIES DESCRIPTION
{NAME => 'personal', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'ROW', REPLICATION_SCOPE => '0', VERSIONS => '5', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => 'FOREVER', KEEP_DELETED_CELLS => 'FALSE', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}
{NAME => 'school', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'ROW', REPLICATION_SCOPE => '0', VERSIONS => '1', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => 'FOREVER', KEEP_DELETED_CELLS => 'FALSE', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}

它显示 VERSIONS =>; '5' 对于 school，它显示 VERSIONS =>; '1'。

如果表已经创建，则可以更改

alter 'student',NAME=>'school',VERSIONS =>3

hbase(main):011:0> describe 'student'
Table student is ENABLED
student
COLUMN FAMILIES DESCRIPTION
{NAME => 'personal', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'ROW', REPLICATION_SCOPE => '0', VERSIONS => '5', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => 'FOREVER', KEEP_DELETED_CELLS => 'FALSE', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}
{NAME => 'school', DATA_BLOCK_ENCODING => 'NONE', BLOOMFILTER => 'ROW', REPLICATION_SCOPE => '0', VERSIONS => '3', COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL => 'FOREVER', KEEP_DELETED_CELLS => 'FALSE', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => 'true'}

它不显示 VERSIONS =>; '3' 按预期用于学校。

将数据放入表中。在同一单元格中输入多次。然后扫描桌子。

put 'student','1','personal:name','kaushik'
put 'student','1','personal:name','kaushik_again'
put 'student','1','school:name','great_school'
put 'student','1','school:name','great_school_again'

scan 'student',{VERSIONS=>10}
ROW  COLUMN+CELL
 1   column=personal:name, timestamp=1443002303208, value=kaushik_again
 1   column=personal:name, timestamp=1443002294049, value=kaushik
 1   column=school:name, timestamp=1443002320753, value=great_school_again
 1   column=school:name, timestamp=1443002311421, value=great_school 

正如预期的那样，它显示了旧价值和新价值。

Answer 2

可以使用 hbase shell 实现相同的效果：

get 'tablename', 'rowid', {COLUMN => 'cf:info', VERSIONS => 3}

上面将显示单元的最大 3 个版本（如果可用）。

Answer 3

您可以指定扫描和获取获得的版本号，它将检索它们：

 HTable tbl = new HTable(tableName);
 Get q= new Get(Bytes.toBytes(key));
 q.setMaxVersions(numberOfVersionsYouWant);
 Result row= tbl.get(q);
 NavigableMap<byte[],NavigableMap<byte[],NavigableMap<Long,byte[]>>> allVersions=row.getMap();