[GitHub] [druid] tianzhipeng-git commented on issue #10380: Druid 0.13.0 NPE problem

[GitBox <gi...@apache.org>]

tianzhipeng-git commented on issue #10380:
URL: https://github.com/apache/druid/issues/10380#issuecomment-693140391


   It's really strange, because I think it is impossible to generate NPE at  [`IncrementalIndex.java:1145->IncrementalIndex.java:1158`](https://github.com/apache/druid/blob/b924f717ee34d7aa48ad50c00eeae8ed84ec960f/processing/src/main/java/org/apache/druid/segment/incremental/IncrementalIndex.java#L1158) of 0.13.0-incubating:
   ```
       public int compare(IncrementalIndexRow lhs, IncrementalIndexRow rhs)
       {
   1158:      int retVal = Longs.compare(lhs.timestamp, rhs.timestamp);
   1159:      int numComparisons = Math.min(lhs.dims.length, rhs.dims.length);
   ```
   (lhs and rhs comes from ConcurrentSkipListMap, which are both not null, and lhs.timestamp is long type)
   
   But line 1159 can generate NPE, maybe the source code messed. (IncrementalIndex.java:1145 is strage too, it looks right if add 1 to 1146 and 1159)
   So in line 1159, the row's dims maybe null,  can you make sure that *all rows in your data have dims values*, without null row?
   
   ----
   In Chinese: 这个报错非常奇怪, 我觉得IncrementalIndex.java:1158不可能产生空指针异常, 代码见上.
   IncrementalIndexRow lhs和rhs都是从ConcurrentSkipListMap中取出来的, 都不可能为空, 且lhs.timestamp是原始long类型也不会报空指针.
   但是我发现1159行其实是可能空指针的, 可能是源码串行了. (IncrementalIndex.java:1145这一行也奇怪, 如果两个行号都加1就看起来都正常了)
   所以如果是1159报空指针, 那么说明lhs或rhs的dims数组是空的, 所以可能是你数据中, 有的数据行, 没有维度列的值? 


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