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Change LOWEST_MAX_STANDARD_ERROR for approx_distinct function #9397

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merged 1 commit into from Nov 25, 2017

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shixuan-fan commented Nov 22, 2017

Maximum number of buckets in HyperLogLog changed from 8192 to 65536,
so now we could support lower max standard errors.

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Looks good, but change the commit message to say: "Reduce lowest standard error for approx_distinct".

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shixuan-fan commented Nov 22, 2017

Thanks for the review! I think it should be "lowest max standard error" :)

@shixuan-fan shixuan-fan force-pushed the shixuan-fan:approx branch from ccaa3df to 411e9c4 Nov 22, 2017

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martint commented Nov 22, 2017

No, the "max" in the names of those constants is wrong. It's not an upper bound on the error. It's a "standard error" (i.e., the standard deviation of the distribution of possible errors). So, this changing the "lowest standard error the function can operate with".

I.e., there's not such a thing as a "max standard error".

Reduce lowest standard error for approx_distinct
Maximum number of buckets in HyperLogLog changed from 8192 to 65536,
so now we could support lower max standard errors.

@shixuan-fan shixuan-fan force-pushed the shixuan-fan:approx branch from 411e9c4 to 2e88e2f Nov 22, 2017

@shixuan-fan shixuan-fan merged commit c2eaae8 into prestodb:master Nov 25, 2017

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