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• Default Value: 100
• Added In: Hive 0.5.0 (replaced by hive.smbjoin.cache.rows in Hive 0.12.0)

How many values in each keys key in the map-joined table should be cached
in cached in memory.

hive.mapjoin.followby.map.aggr.hash.percentmemory

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The number means after how many rows processed it needs to check the memory usage.

hive.smbjoin.cache.rows

• Default Value: 10000
• Added In: Hive 0.12.0 with HIVE-4440 (replaces hive.mapjoin.bucket.cache.size)

How many rows with the same key value should be cached in memory per sort-merge-bucket joined table.

hive.mapjoin.optimized.keys

• Default Value: true
• Added In: Hive 0.13.0 with HIVE-6429 and HIVE-6188

Whether a MapJoin hashtable should use optimized (size-wise) keys, allowing the table to take less memory. Depending on the key, memory savings for the entire table can be 5-15% or so.

hive.mapjoin.lazy.hashtable

• Default Value: true
• Added In: Hive 0.13.0 with HIVE-6418 and HIVE-6188

Whether a MapJoin hashtable should deserialize values on demand. Depending on how many values in the table the join will actually touch, it can save a lot of memory by not creating objects for rows that are not needed. If all rows are needed, obviously there's no gain.

hive.optimize.skewjoin

• Default Value: false
• Added In: Hive 0.6.0

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