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Reduce deduplication merges two RSs (reduce sink operators) by moving key/parts/reducer-num of the child RS to parent RS. That means if reducer-num of the child RS is fixed (order by or forced bucketing) and small, it can make very slow, single MR. The optimization will be disabled if number of reducers is less than specified value.

hive.optimize.correlation

• Default Value: false
• Added In: Hive 0.12.0 with HIVE-2206

Exploit intra-query correlations. For details see the Correlation Optimizer design document.

hive.exec.dynamic.partition

• Default Value: false
• Added In:

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