Hi @ToddP  Can you try after setting below? set hive.vectorized.execution.enabled=false; ... View more

Yes, there are lot of places to check but without knowing what are you looking for you will be lost.   You can start with what you see on screen / console where you run the query.   In beeline you see tez job summary which has lot of details to look at.   example of one of the tuning guide is below   https://community.cloudera.com/t5/Community-Articles/Demystify-Apache-Tez-Memory-Tuning-Step-by-Step/ta-p/245279     Update: I see you are using cdh6 which does not have tez.     You can refer below link for cdh https://docs.cloudera.com/documentation/enterprise/6/6.1/topics/admin_hive_tuning.html#concept_u51_lkv_cv ... View more

Hi @Andyjmoss    As you already pointed https://community.cloudera.com/t5/Support-Questions/How-are-number-of-mappers-determined-for-a-query... There is no limit per query, you can only adjust max and min grouping size to play around on mapper tasks. Would this then impact the structure of data stored by my data? No this only affects how much data each map task will get. ... View more