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https://issues.apache.org/jira/browse/HBASE-15676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15259722#comment-15259722
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Heng Chen commented on HBASE-15676:
-----------------------------------

{code}
+      // This shift is idempotent - always end up with 0 and -1 as mask values.
+      for (int j = 0; j < fuzzyData.getSecond().length; j++) {
+        fuzzyData.getSecond()[j] >>>= 2;
+      }
{code}
What's the code used for? 

{code}
  /**
   * We need to preprocess mask array, as since we treat 0's as unfixed 
positions and -1 (0xff) as
   * fixed positions
   * @param mask
   * @return mask array
   */
  private byte[] preprocessMask(byte[] mask) {
{code}

Comments should be modified?




> FuzzyRowFilter fails and matches all the rows in the table if the mask 
> consists of all 0s
> -----------------------------------------------------------------------------------------
>
>                 Key: HBASE-15676
>                 URL: https://issues.apache.org/jira/browse/HBASE-15676
>             Project: HBase
>          Issue Type: Bug
>          Components: Filters
>    Affects Versions: 2.0.0, 0.98.13, 1.0.2, 1.2.0, 1.1.1
>            Reporter: Rohit Sinha
>         Attachments: hbase-15676-v1.patch, hbase-15676-v2.patch
>
>
> While using FuzzyRowFilter we noticed that if the mask array consists of all 
> 0s (fixed) the FuzzyRowFilter matches all the rows in the table. We noticed 
> this on HBase 1.1, 1.2 and higher.
> After some digging we suspect that this is because of isPreprocessedMask() 
> check which is used in preprocessMask() which was added here: 
> https://issues.apache.org/jira/browse/HBASE-13761
> If the mask consists of all 0s then the isPreprocessedMask() returns true and 
> the preprocessing which responsible for changing 0s to -1 doesn't happen and 
> hence all rows are matched in scan.
> This scenario can be tested in TestFuzzyRowFilterEndToEnd#testHBASE14782() If 
> we change the 
> byte[] fuzzyKey = Bytes.toBytesBinary("\\x00\\x00\\x044");
> byte[] mask = new byte[] {1,0,0,0};
> to 
> byte[] fuzzyKey = Bytes.toBytesBinary("\\x9B\\x00\\x044e");
> byte[] mask = new byte[] {0,0,0,0,0};
> We expect one match but this will match all the rows in the table. 



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