问题描述

对一张log表按时间过滤

正常数据的话,每行有一个时间戳列timestamp作为操作时间,按这个列值过滤出特定时间段的log信息

但是不知怎么的log表中多了一些垃圾数据(不一定是垃圾数据,只是没有timestamp这个字段)。

过滤第一天的话会有5800条没有操作时间(timestamp),

过滤第二天的时候还是有5800条没有操作时间的,

过滤前两天的时候还是5800条。

问题分析

问题很明显了,就是当某一行没有要过滤的字段时,SingleColumnValueFilter是默认这一行符合过滤条件的。

接下来就要让SingleColumnValueFilter在判断的时候把这个策略改改。

查看源码发现是有方法可以更改这个策略的

代码展现

在SingleColumnValueFilter的源码开头的一段注释中(加粗加大的位置)说明了方法

/** * This filter is used to filter cells based on value. It takes a {@link CompareFilter.CompareOp} * operator (equal, greater, not equal, etc), and either a byte [] value or * a ByteArrayComparable. * 
 * If we have a byte [] value then we just do a lexicographic compare. For * example, if passed value is 'b' and cell has 'a' and the compare operator * is LESS, then we will filter out this cell (return true).  If this is not * sufficient (eg you want to deserialize a long and then compare it to a fixed * long value), then you can pass in your own comparator instead. * 
 * You must also specify a family and qualifier.  Only the value of this column * will be tested. When using this filter on a {@link Scan} with specified * inputs, the column to be tested should also be added as input (otherwise * the filter will regard the column as missing). * 
 * To prevent the entire row from being emitted if the column is not found * on a row, use {@link #setFilterIfMissing}. * Otherwise, if the column is found, the entire row will be emitted only if * the value passes.  If the value fails, the row will be filtered out. * 
 * In order to test values of previous versions (timestamps), set * {@link #setLatestVersionOnly} to false. The default is true, meaning that * only the latest version's value is tested and all previous versions are ignored. * 
 * To filter based on the value of all scanned columns, use {@link ValueFilter}. */

更改代码

SingleColumnValueFilter f1 = new SingleColumnValueFilter(Bytes.toBytes(FAMILY), Bytes.toBytes("timestamp"), CompareOp.GREATER_OR_EQUAL, Bytes.toBytes(starttime));SingleColumnValueFilter f2 = new SingleColumnValueFilter(Bytes.toBytes(FAMILY), Bytes.toBytes("timestamp"), CompareOp.LESS, Bytes.toBytes(endtime));f1.setFilterIfMissing(true);　　//true 跳过改行;false 通过该行f2.setFilterIfMissing(true);filters.add(f1);filters.add(f2);

反思

一开始打算继承出一个新类,然后重写部分方法,不过好像还是这样更灵活一些