physicalplan: add support for multi-stage execution of aggregate func…

[piao88]

Needed for #58347

This commit adds support for muti-stage execution of the following aggregate functions , sqrdiff stddev_pop var_pop regr_count regr_avgx regr_avgy regr_sxx regr_syy. besides , I add the aggregate functions regr_sx( Calculates sum of the independent variable) and regr_sy( Calculates sum of the dependent variable.) in support of building regr_sxx and regr_syy muti-stage function. The rest functions (corr ,covar_pop, covar_samp,regr_intercept,regr_r2,regr_slope,regr_sxy ) are not finished yet.

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❌ Piao ZhiHuan
❌ piao88

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[RaduBerinde]

This is great, thanks for the contribution! We will, however need some logictests for all these functions. The logictests are powerful because they run in many configurations, including "local" (where multi-stage won't be planned) and "fakedist" (which fakes a random distribution of table data in each run); so they would automatically cross-check the results with multi-stage planning against those without it.

[piao88]

hi,thanks for your review !
I find some bugs about decimal precision in this commit . It has a little different between the result of miti-stage aggregate function and "local" function . (e.g. 82499.99999999999999999965 is the result of sqrdiff in "muti-stage" and 82499.99999999999999999985 is the result in "local" ) . I will take some days to fix it .

[RaduBerinde]

Those kind of differences are expected since the result is calculated through a different sequence of operations. The logictests have a tolerance for float results (https://github.com/cockroachdb/cockroach/blob/master/pkg/sql/logictest/logic.go#L2881).

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[RaduBerinde]

There are a lot of TestDistAggregationTable failures; perhaps the tolerated errors in those tests need to be relaxed a bit (though they've been sufficient so far).

Please bump the Version in execinfra/version.go (and add a note in the comment).

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @piao88 and @yuzefovich)

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pkg/sql/logictest/testdata/logic_test/distsql_agg, line 660 at r4 (raw file):

# Test muti-stage aggregate functions for #58347 (add support for multi-stage execution of aggregate functions).
statement ok
CREATE TABLE t (a INT, b INT, c FLOAT, d DECIMAL, PRIMARY KEY (a, b, c, d))

This test would be better in the aggregate file. We don't need the part starting from ALTER TABLE - that file runs under fakedist configuration which will pretend there is a random multi-node distribution of data each time it is run. By the way, some existing tests in that file now fail.

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pkg/sql/sem/builtins/aggregate_builtins.go, line 1957 at r4 (raw file):

}

func newFloatFinalRegressionSyyAggregate(

Why do we need these two variants if they're the same thing?

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pkg/sql/sem/builtins/aggregate_builtins.go, line 3590 at r4 (raw file):

}

func newFloatFinalStddevPopAggregate(

Isn't this exactly the same with newDecimalFinalStdDevAggregate? Why not use the existing one? I would review all the new ones and keep only those for which we can't use an existing built-in.

[yuzefovich]

#58347 has been fixed on master.