ClickHouse/01017_uniqCombined_memory_usage.reference at 655ce5b6a7cbf313fdbcb4ea761d82985a680092 - ClickHouse - gitea@var1able.network

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Azat Khuzhin e373862c83 Do not use more then 98K of memory for uniqCombined*

uniqCombined() uses hashtable for medium cardinality, and since
HashTable resize by the power of 2 (well actually HashTableGrower grows
double by the power of 2, hence HashTableGrower::increaseSize() should
be overwritten to change this), with 1<<13 (default for uniqCombined)
and UInt64 HashValueType, the HashTable will takes:

  getBufferSizeInBytes() == 131072

While it should be not greater then sizeof(HLL) ~= 98K, so reduce the
maximum cardinality for hashtable to 1<<12 with UInt64 HashValueType and
to 1<13 with UInt32, overwrite HashTableGrower::increaseSize() and cover
this using max_memory_usage.

Refs: https://github.com/ClickHouse/ClickHouse/pull/7221#issuecomment-539672742

v2: cover uniqCombined() with non-default K

2019-10-09 02:39:23 +03:00

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 UInt32
 
 UInt64
 
 K=16
 UInt32
 
 UInt64
 
 K=18
 UInt32
 1638400
 UInt64