hbase scan中匪夷所思的SingleColumnValueFilter和COLUMNS

假设关系型数据库中存在如下表(test_row_key)------------------------------------------TIME_ID    AREA_ID       INDEX1.......................................... 201206        730    201206730 201206        731    201206731 201207        730    201207730 201207        731    201207731 201207        732    201207732  让我们将数据导入hbase(测试环境Version 0.94.3, r1408904)问题重现// select TIME_ID, AREA_ID, INDEX1 from test_row_key where TIME_ID = 201206 and AREA_ID = 730// 应该返回1行数据scan 'test_row_key', {COLUMNS => ['cf:TIME_ID','cf:AREA_ID','cf:INDEX1'], FILTER => "(SingleColumnValueFilter('cf', 'TIME_ID', =, 'binary:201206')) AND (SingleColumnValueFilter('cf', 'AREA_ID', =, 'binary:730'))" } // select AREA_ID, INDEX1          from test_row_key where TIME_ID = 201206 and AREA_ID = 730// 返回2行数据??scan 'test_row_key', {COLUMNS => ['cf:AREA_ID','cf:INDEX1'],              FILTER => "(SingleColumnValueFilter('cf', 'TIME_ID', =, 'binary:201206')) AND (SingleColumnValueFilter('cf', 'AREA_ID', =, 'binary:730'))" } // select INDEX1                   from test_row_key where TIME_ID = 201206 and AREA_ID = 730// 返回2行数据??scan 'test_row_key', {COLUMNS => ['cf:INDEX1'],                           FILTER => "(SingleColumnValueFilter('cf', 'TIME_ID', =, 'binary:201206')) AND (SingleColumnValueFilter('cf', 'AREA_ID', =, 'binary:730'))" }  结论只有当COLUMNS中包含SingleColumnValueFilter提到的字段时, 该SingleColumnValueFilter才有效的
改为SingleColumnValueExcludeFilter, 这时只会返回除开AREA_ID和TIME_ID的字段, 但记录数是对的HBase JIRA中有人对这种匪夷所思的行为产生的质疑
只有当COLUMNS中包含SingleColumnValueFilter提到的字段时, 该SingleColumnValueFilter才有效的
 
SingleColumnValueFiltershould be able to find the column value even when it's not specifically addedas input on the scan.
Wheneverapplying a SingleColumnValueFilter to a Scan that has specific columns as it'sinput (but not the column to be checked in the Filter), the Filter won't beable to find the value that it should be checking.
Forexample, let's say we want to do a scan, but we only need COLUMN_2 columns.Furthermore, we only want rows that have a specific value for COLUMN_1. Usingthe following code won't do the trick:
Scan scan = new Scan();
scan.addColumn(FAMILY,COLUMN_2);
SingleColumnValueFilter filter = new SingleColumnValueFilter(FAMILY, COLUMN_1,CompareOp.EQUAL, TEST_VALUE);
filter.setFilterIfMissing(true);
scan.setFilter(filter);
However,we can make it work when specifically also adding the tested column as an inputcolumn:
scan.addColumn(FAMILY,COLUMN_1);
Is this by design?Personally I think that adding a filter with columns tests should not botherthe user to check that it's also on the input. It is prone to bugs.
 
有人回复说:
Itsby design. High-level in the Scan object you say what you are interested in andthen the filter works against the Scan specification.
 
作者修改了SingleColumnValueFilter.java的doc注释
Whenusing this filter on a Scan with specified inputs, the column to be testedshould also be added as input (otherwise the filter will regard the column asmissing).
 
于是作者写了一个新的SingleColumnValueExcludeFilter,用于做单列的值过滤, 但是不查询出这个列的值
Add a new Filter thatchecks a single column value but does not emit it.
A Filter that checks a single column value,but does not emit the tested column. This will enable a performance boost overSingleColumnValueFilter, if the tested column value is not actually needed asinput (besides for the filtering itself).