[GitHub] [phoenix] twdsilva commented on a change in pull request #515: PHOENIX-5318 Slots passed to SkipScan filter is incorrect for desc pr…

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twdsilva commented on a change in pull request #515: PHOENIX-5318 Slots passed to SkipScan filter is incorrect for desc pr…
URL: https://github.com/apache/phoenix/pull/515#discussion_r291697101
 
 

 ##########
 File path: phoenix-core/src/main/java/org/apache/phoenix/query/KeyRange.java
 ##########
 @@ -108,6 +109,34 @@ public KeyRange apply(byte[] input) {
         }
     };
 
 
 Review comment:
   @dbwong  ```KeyRange.COMPARATOR.reversed()``` will not give the correct behavior. 
   
   For eg for the query Where COL1='1' OR COL1='12' OR COL1='2'
   the key range before sorting is
   
   ```
   0 = {KeyRange@8864} "\xCE" -> "1"
   1 = {KeyRange@8865} "\xCE\xCD" -> "12" 
   2 = {KeyRange@8866} "\xCD" -> "2"
   ```
   
   Sorting using  ```KeyRange.COMPARATOR``` gives the following which isn't correct.
   ```
   0 = {KeyRange@8879} "\xCD" -> "2"
   1 = {KeyRange@8880} "\xCE" -> "1"
   2 = {KeyRange@8881} "\xCE\xCD" -> "12"
   ```
   Using ```KeyRange.COMPARATOR.reverse()``` just reverses the following order which isn't correct.
   
   We need "12" to sort before "1" as thats how its stored on disk. Using ```DescVarLengthFastByteComparisons``` gives  the correct ordering:
   ```
   0 = {KeyRange@8899} "\xCD" -> "2"
   1 = {KeyRange@8900} "\xCE\xCD" -> "12
   2 = {KeyRange@8901} "\xCE" -> "1"
   ```

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