Optimize aggregate accumulators #323
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Scalar tables used for the hash aggregate with grouping labels are currently very wasteful because of the dynamic functions they create for each output group. Each function ends up as a new object on the heap, so for queries where output groups have high cardinality we end up using a lot of memory. This commit fixes that by converting accumulators to structs, so that functions between accumulator instances do not end up as heap-allocated objects. Signed-off-by: Filip Petkovski <[email protected]>
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Signed-off-by: Filip Petkovski <[email protected]>
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Scalar tables used in the hash aggregate with grouping labels are currently very wasteful because of the dynamic functions they create for each output group. Each function ends up as a new object on the heap, so for queries where output groups have high cardinality we end up using a lot of memory.
This commit fixes that by converting accumulators to structs, so that functions between accumulator instances do not end up as heap-allocated objects.
Here is an extreme case where accumulators took 12GB of heap space:
