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Move-away "uniqCombined" as a separate aggregated function #3406

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merged 20 commits into from
Nov 22, 2018

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abyss7
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@abyss7 abyss7 commented Oct 17, 2018

Accepts single param - the HLL precision.

AggregateFunctionPtr createAggregateFunctionUniqCombined(
const std::string & name, const DataTypes & argument_types, const Array & params)
{
UInt8 precision = 17; /// default value - must correlate with default ctor of |AggregateFunctionUniqCombinedData|
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If it MUST be correlated it's better to set named constant and use it both here and in ctor.

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It correlates with a hardcoded union member initialization, the constant won't help - so I left the comment. The code now looks like: AggregateFunctionUniqCombinedDataWithKey() : set_17() {} - Also I can use a macro-definition as constant, if it's better.

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My point is there should be only one place there magic number 17 set.

SELECT Y, uniqCombined(X) FROM (SELECT number AS X, (3*X*X - 7*X + 11) % 37 AS Y FROM system.numbers LIMIT 15) GROUP BY Y;
SELECT Y, uniqCombined(X) FROM (SELECT number AS X, (3*X*X - 7*X + 11) % 37 AS Y FROM system.numbers LIMIT 3000) GROUP BY Y;
SELECT Y, uniqCombined(X) FROM (SELECT number AS X, (3*X*X - 7*X + 11) % 37 AS Y FROM system.numbers LIMIT 1000000) GROUP BY Y;
SELECT Y, uniqCombined(15)(X) FROM (SELECT number AS X, (3*X*X - 7*X + 11) % 37 AS Y FROM system.numbers LIMIT 15) GROUP BY Y;
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Would it change default behavior? What if someone already use uniqCombined without parameter. Would he (or she :) ) get the same values after update?

@alexey-milovidov alexey-milovidov merged commit 89e3c5c into ClickHouse:master Nov 22, 2018
alexey-milovidov added a commit that referenced this pull request Nov 22, 2018
alexey-milovidov added a commit that referenced this pull request Nov 23, 2018
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https://gist.github.com/alexey-milovidov/9cbbc2916f8d946594049d424487e458

Now the uniqHLL12 function can be considered obsolete.

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4 participants