9d2f8043_Troubleshooting_Impala__Recommendation
[Symptom] Joins fail to complete. [Explanation] There may be insufficient memory. During a join, data from the second, third, and so on sets to be joined is loaded into memory. If Impala chooses an inefficient join order or join mechanism, the query could exceed the total memory available. [Recommendation] 
Start by gathering statistics with the COMPUTE STATS statement for each table involved in the join. Consider specifying the [SHUFFLE] hint so that data from the joined tables is split up between nodes rather than broadcast to each node. If tuning at the SQL level is not sufficient, add more memory to your system or join smaller data sets.
Troubleshooting Impala